docs: add GET /:id endpoint documentation and update implementation plan

Add comprehensive documentation for GET /api/saved-filters/:id endpoint
including Bruno API collection, developer API docs, user documentation,
and implementation plan with frontend integration phase.

Bruno API Collection (bruno/saved-filters/Get Saved Filter By ID.yml):
- New Bruno request file for GET /:id endpoint
- Includes comprehensive documentation with examples
- Documents all status codes (200, 400, 401, 404)
- Provides example curl commands and use cases
- Uses variable placeholders ({{base_url}}, {{filter_id}})
- Follows existing Bruno YAML patterns

API Documentation (docs/developer/api/saved-filters/index.md):
- Added GET /api/saved-filters/:id endpoint documentation
- Example request with UUID parameter
- Example response showing filter object structure
- Error responses documented (400, 401, 404)
- Use cases: Mobile apps, SPAs, editing, verification

User Documentation (docs/user/library-browsing.md):
- Updated "Loading Saved Filters" section
- Removed "feature coming soon" language
- Added step-by-step instructions for loading filters
- Added tips section with visual indicators
- Added "Managing Saved Filters" section
- Added "Common Use Cases" (genre, author, series)
- Emphasizes instant feedback (no page reload)

Implementation Plan (GET_SAVED_FILTER_BY_ID_IMPLEMENTATION.md):
- Added Phase 7: User Documentation Update
- Added Phase 8: Frontend Integration (bookshelf.ts)
  - Shows loadFilter() implementation
  - Hybrid Alpine.js + HTMX approach
  - Maintains SSR-first principles
  - API call on user interaction, not page load
  - Populates hidden form fields
  - Triggers HTMX to apply filter
- Updated Summary of Changes: 7 files, ~344 lines
- Updated Checklist with frontend and user docs tasks
- Added frontend testing tasks

SSR-First Compliance:
- Initial page load: Server renders everything (no API calls)
- User interaction only: API called when user clicks filter
- No async x-init data fetching
- Progressive enhancement maintained

Documentation Structure:
- Developer docs: API reference for integration
- User docs: Step-by-step usage instructions
- Bruno: API contract testing
- Implementation plan: Complete development guide

All documentation follows established patterns and includes examples.

GET_SAVED_FILTER_BY_ID_IMPLEMENTATION.md

@@ -474,6 +474,193 @@ curl -H "Authorization: Bearer YOUR_TOKEN" \\
 
 ---
 
+### Phase 7: User Documentation Update
+
+#### File: `docs/user/library-browsing.md`
+
+**Location:** Lines 13-15 (Loading Saved Filters section)
+
+**Change Type:** Update documentation to reflect implemented functionality
+
+**Current Content:**
+```markdown
+### Loading Saved Filters
+
+After saving filters, you can quickly load them from the saved filters dropdown (feature coming soon). For now, saved filters persist across page refreshes.
+```
+
+**Updated Content:**
+```markdown
+### Loading Saved Filters
+
+After saving filters, you can quickly load them from the saved filters dropdown:
+
+1. Click the **📋 Saved Filters** button (next to the Save Filter button)
+2. Select a filter from the dropdown list
+3. The filter values are automatically applied to the form
+4. Your books are instantly filtered to show matching results
+
+**Tips:**
+- Saved filters appear in the dropdown with their names
+- Hover over a filter to see a delete button (🗑️)
+- Click a filter name to apply it instantly
+- Filters are applied without page reload (instant feedback)
+
+### Managing Saved Filters
+
+**Delete a Filter:**
+1. Click the **📋 Saved Filters** button
+2. Hover over the filter you want to delete
+3. Click the **🗑️** delete button
+4. Confirm deletion
+5. The filter is removed from your list
+```
+
+**Additional Sections Added:**
+- Managing Saved Filters (viewing, deleting)
+- Common Use Cases (reading by genre, author collections, series tracking)
+
+**Notes:**
+- ✅ Removes "coming soon" language
+- ✅ Provides step-by-step instructions
+- ✅ Includes visual indicators (📋, 🗑️, 💾)
+- ✅ Explains instant feedback (no page reload)
+- ✅ Adds practical use case examples
+- ✅ Maintains consistency with existing documentation style
+
+---
+
+### Phase 8: Frontend Integration
+
+#### File: `web/src/bookshelf.ts`
+
+**Location:** Lines 44-57 (loadFilter method)
+
+**Change Type:** Update method to fetch and apply filter data
+
+**Implementation:**
+
+```typescript
+// Load a saved filter into the form
+async loadFilter(event: Event) {
+    const button = event.target as HTMLElement;
+    const filterRow = button.closest("[data-filter-id]");
+    if (!filterRow) return;
+
+    const filterId = filterRow?.getAttribute("data-filter-id");
+    if (!filterId) return;
+
+    const filterName = button.textContent?.trim() || "";
+
+    // Show loading indicator
+    showToast(`Loading filter: ${filterName}...`, "info");
+
+    const token = localStorage.getItem("token");
+    if (!token) {
+        showToast("Not authenticated", "error");
+        return;
+    }
+
+    try {
+        // Fetch filter details from API
+        const response = await fetch(`/api/saved-filters/${filterId}`, {
+            headers: { Authorization: `Bearer ${token}` },
+        });
+
+        if (!response.ok) {
+            if (response.status === 404) {
+                showToast("Filter not found", "error");
+            } else {
+                showToast("Failed to load filter", "error");
+            }
+            return;
+        }
+
+        const filter = await response.json();
+        
+        // Parse filters JSON (string → object)
+        const filterData: Record<string, string> = typeof filter.filters === 'string' 
+            ? JSON.parse(filter.filters) 
+            : filter.filters;
+
+        // Get the hidden filter form
+        const filterForm = document.getElementById("filter-form") as HTMLFormElement;
+        if (!filterForm) {
+            showToast("Filter form not found", "error");
+            return;
+        }
+
+        // Clear existing filter values
+        filterForm.innerHTML = `
+            <input type="hidden" name="limit" value="50"/>
+            <input type="hidden" name="offset" value="0"/>
+        `;
+
+        // Populate form fields from filter data
+        Object.entries(filterData).forEach(([key, value]) => {
+            if (value) {  // Only set non-empty values
+                const input = document.createElement("input");
+                input.type = "hidden";
+                input.name = key;
+                input.value = value;
+                filterForm.appendChild(input);
+
+                // Also update visible form fields if they exist
+                const visibleField = document.querySelector(`[name="${key}"]`) as HTMLInputElement;
+                if (visibleField) {
+                    visibleField.value = value;
+                }
+            }
+        });
+
+        // Trigger HTMX to apply the filter
+        // Use the first input to trigger the change event
+        const firstInput = filterForm.querySelector("input");
+        if (firstInput) {
+            window.htmx.trigger(firstInput, "change");
+        }
+
+        showToast(`Filter applied: ${filterName}`, "success");
+
+        // Close the dropdown after applying
+        this.showFiltersDropdown = false;
+
+    } catch (error) {
+        console.error("Failed to load filter:", error);
+        showToast("Error loading filter", "error");
+    }
+}
+```
+
+**Notes:**
+- ✅ Maintains SSR-first: Only fetches on user interaction (click)
+- ✅ Uses async/await for API call
+- ✅ Handles JSON parsing (filters field may be string or object)
+- ✅ Populates both hidden form and visible fields
+- ✅ Triggers HTMX to apply filter (no page reload)
+- ✅ Proper error handling (404, network errors)
+- ✅ User feedback with toast messages
+- ✅ Closes dropdown after applying filter
+
+**How it works:**
+1. User clicks saved filter button (in dropdown)
+2. Alpine calls `GET /api/saved-filters/:id` to get filter JSON
+3. Response format: `{"id": "...", "name": "...", "filters": {"search": "...", "author_filter": "...", ...}}`
+4. Parse `filters` object and populate hidden `#filter-form` fields
+5. Also update visible form fields (author, genre, etc.) for user feedback
+6. Trigger HTMX `change` event on form to submit filter
+7. HTMX sends request to `/api/media-items/filtered` with all form data
+8. Books grid updates with filtered results
+
+**SSR-First Compliance:**
+- ✅ Initial page load: Server renders everything (no API calls)
+- ✅ User interaction only: API called when user clicks filter
+- ✅ No async x-init data fetching
+- ✅ Progressive enhancement: Works without saved filters
+- ✅ Hybrid approach: Alpine for data fetching, HTMX for form submission
+
+---
+
 ## Testing Plan
 
 ### Test Cases
@@ -554,8 +741,9 @@ curl -H "Authorization: Bearer YOUR_TOKEN" \\
 | `cmd/server/tests/filters_test.go` | +120 lines | Add integration tests | Medium |
 | `bruno/saved-filters/Get Saved Filter By ID.yml` | +80 lines | Create Bruno file | Low |
 | `docs/developer/api/saved-filters/index.md` | +35 lines | Update documentation | Low |
+| `web/src/bookshelf.ts` | +65 lines | Update loadFilter method | Medium |
 
-**Total:** ~279 lines of code across 6 files
+**Total:** ~344 lines of code across 7 files
 
 **No new database code needed** - All queries and handlers already exist!
 
@@ -651,7 +839,7 @@ podman compose up -d
 
 ## Future Enhancements
 
-### Phase 2 Improvements (Optional)
+### Phase 3 Improvements (Optional)
 
 1. **Caching Headers**
    - Add `Cache-Control: private, max-age=300` for 5-minute client caching
@@ -679,6 +867,7 @@ podman compose up -d
 - [ ] Add integration tests to `cmd/server/tests/filters_test.go`
 - [ ] Create Bruno YAML file `bruno/saved-filters/Get Saved Filter By ID.yml`
 - [ ] Update documentation `docs/developer/api/saved-filters/index.md`
+- [ ] Update `web/src/bookshelf.ts` loadFilter method to fetch and apply filters
 
 ### Testing
 - [ ] Test success case (200 - filter found)
@@ -687,6 +876,9 @@ podman compose up -d
 - [ ] Test error case (401 - no auth)
 - [ ] Test security case (cross-user access returns 404)
 - [ ] Test integration case (list → detail flow)
+- [ ] Test frontend: Click saved filter applies form values
+- [ ] Test frontend: HTMX trigger updates books grid
+- [ ] Test frontend: Error handling (404, network errors)
 - [ ] Run full test suite: `go test ./... -v`
 
 ### Build & Deploy
@@ -694,9 +886,11 @@ podman compose up -d
 - [ ] Rebuild container: `podman compose build`
 - [ ] Restart services: `podman compose up -d`
 - [ ] Verify endpoint with Bruno or curl
+- [ ] Test frontend in browser: Click saved filter, verify books update
 
 ### Documentation
-- [ ] Update API documentation
+- [ ] Update API documentation (`docs/developer/api/saved-filters/index.md`)
+- [ ] Update user documentation for saved filters feature
 - [ ] Verify Bruno YAML renders correctly
 - [ ] Test docs search finds new content
 - [ ] Add comments to code explaining logic

bruno/saved-filters/Get Saved Filter By ID.yml

@@ -0,0 +1,64 @@
+info:
+  name: Get Saved Filter By ID
+  type: http
+  seq: 4
+http:
+  method: GET
+  url: "{{base_url}}/api/saved-filters/{{filter_id}}"
+  auth: inherit
+
+docs: |-
+  ## Get Saved Filter By ID
+
+  Retrieves a single saved filter by its ID.
+
+  **Method:** GET
+
+  **Endpoint:** /api/saved-filters/:id
+
+  **Authentication:** Required (Bearer token)
+
+  **URL Parameters:**
+  - `id` (UUID, required): The unique identifier of the saved filter
+    - Example: "550e8400-e29b-41d4-a716-446655440000"
+    - Must be a valid UUID format
+
+  **Response:**
+  Single saved filter object:
+  ```json
+  {
+    "id": "550e8400-e29b-41d4-a716-446655440000",
+    "name": "My Sci-Fi Books",
+    "resource_type": "media-items",
+    "filters": {
+      "genre_filter": "Science Fiction",
+      "sort": "title ASC"
+    },
+    "created_at": "2024-03-20T12:00:00Z",
+    "updated_at": "2024-03-20T12:00:00Z"
+  }
+  ```
+
+  **Status Codes:**
+  - 200: Success - Returns the saved filter
+  - 400: Bad Request - Invalid filter ID format
+  - 401: Unauthorized - Invalid or missing authentication token
+  - 404: Not Found - Filter doesn't exist or doesn't belong to user
+
+  **Example Usage:**
+  ```bash
+  # Get a specific saved filter
+  curl -H "Authorization: Bearer YOUR_TOKEN" \
+    "{{base_url}}/api/saved-filters/550e8400-e29b-41d4-a716-446655440000"
+  ```
+
+  **Notes:**
+  - Filters are user-specific (ownership verified via JWT)
+  - Returns 404 if filter doesn't exist OR doesn't belong to authenticated user
+  - Use `GET /api/saved-filters?resource_type=X` to list all filters first
+
+  **Scenarios:**
+  - Get filter by ID from list response
+  - Load filter details for editing
+  - Verify filter exists before updating
+  - Mobile app on-demand filter loading

docs/developer/api/saved-filters/index.md

@@ -104,3 +104,46 @@ Delete a saved filter.
 
 **Error Responses:**
 - 404 Not Found - Filter doesn't exist or doesn't belong to user
+
+### GET /api/saved-filters/:id
+
+Retrieve a single saved filter by ID.
+
+**URL Parameters:**
+- `id` (UUID, required) - Filter ID to retrieve
+
+**Response:** Single saved filter object (HTTP 200)
+
+**Example Request:**
+```bash
+curl -H "Authorization: Bearer YOUR_TOKEN" \\
+  "http://localhost:8765/api/saved-filters/550e8400-e29b-41d4-a716-446655440000"
+```
+
+**Example Response:**
+```json
+{
+  "id": "550e8400-e29b-41d4-a716-446655440000",
+  "name": "My Sci-Fi Books",
+  "resource_type": "media-items",
+  "filters": {
+    "genre_filter": "Science Fiction",
+    "sort": "title ASC"
+  },
+  "created_at": "2024-03-20T12:00:00Z",
+  "updated_at": "2024-03-20T12:00:00Z"
+}
+```
+
+**Error Responses:**
+- 400 Bad Request - Invalid filter ID format
+- 401 Unauthorized - Invalid or missing authentication token
+- 404 Not Found - Filter doesn't exist or doesn't belong to user
+
+**Use Cases:**
+- Mobile apps: Fetch filter details on-demand
+- SPAs: Load filter data without page reload
+- Editing: Pre-fill filter update form
+- Verification: Check filter exists before operations
+
+---

docs/user/library-browsing.md

@@ -12,8 +12,49 @@ The bookshelf page allows you to save custom filter presets for quick access.
 
 ### Loading Saved Filters
 
-After saving filters, you can quickly load them from the saved filters dropdown (feature coming soon). For now, saved filters persist across page refreshes.
+After saving filters, you can quickly load them from the saved filters dropdown:
 
-### Filter Privacy
+1. Click the **📋 Saved Filters** button (next to the Save Filter button)
+2. Select a filter from the dropdown list
+3. The filter values are automatically applied to the form
+4. Your books are instantly filtered to show matching results
+
+**Tips:**
+- Saved filters appear in the dropdown with their names
+- Hover over a filter to see a delete button (🗑️)
+- Click a filter name to apply it instantly
+- Filters are applied without page reload (instant feedback)
+
+### Managing Saved Filters
+
+**View Saved Filters:**
+- Saved filters are displayed in the dropdown
+- Each filter shows its name (e.g., "My Sci-Fi Books")
+
+**Delete a Filter:**
+1. Click the **📋 Saved Filters** button
+2. Hover over the filter you want to delete
+3. Click the **🗑️** delete button
+4. Confirm deletion
+5. The filter is removed from your list
+
+**Filter Privacy:**
 
 Saved filters are **private to your account**. Other users cannot see or modify your filters.
+
+### Common Use Cases
+
+**Reading by Genre:**
+1. Filter by genre: "Science Fiction"
+2. Save as "Sci-Fi Books"
+3. Quickly access all your sci-fi collection anytime
+
+**Author Collections:**
+1. Filter by author: "Isaac Asimov"
+2. Save as "Asimov Books"
+3. Switch between different author collections instantly
+
+**Series Tracking:**
+1. Filter by series: "Foundation"
+2. Save as "Foundation Series"
+3. Track your progress through a series