feat: implement collection library filter with WebSocket improvements and test coverage

This commit adds comprehensive functionality for filtering collections by library,
improves WebSocket real-time updates with user activity detection, and adds
extensive test coverage.

## Core Features

### Collection Library Filter
- Added library_id parameter to media-items search API
- Collections can now be filtered by specific library
- Toggle UI component for enabling/disabling library filter
- Default state is "checked" when library_id is present
- Consistent behavior across partial and fuzzy search modes

### WebSocket Auto-Reload Mitigation
- Added user activity detection to prevent disruptive page reloads
- Checks if user is actively typing in INPUT/TEXTAREA/SELECT elements
- Skips auto-reload when user is interacting with form elements
- Toast notifications still show for awareness
- Prevents data loss during editing operations

## Implementation Changes

### Backend
- internal/database/queries.sql.go: Added library filter support to search queries
- internal/handlers/media.go: Enhanced search with library_id parameter validation
- internal/handlers/collections.go: Updated collection handlers with library filtering
- internal/sync/websocket.go: Improved broadcast mechanism with user-scoped updates
- internal/router/frontend.go: Pass libraryID to collection templates

### Frontend
- templates/collections.templ: Added library filter toggle UI component
- web/src/collections.ts: TypeScript implementation with WebSocket integration
- templates/collections_templ.go: Generated template code

### Testing
- cmd/server/tests/search_test.go: Added TestCollectionSearchLibraryFilter
- cmd/server/tests/websocket_test.go: Added TestWebSocketUserScopedBroadcast
- New helper functions for creating libraries and media items via API
- Comprehensive test coverage for library filtering and user-scoped broadcasts

## API Documentation Updates

### Bruno Tests (Comprehensive Documentation)
- bruno/collections/*: Added detailed API documentation for all collection endpoints
- bruno/devices/*: Added device management and sync API documentation
- bruno/devices/kobo/api.yml: Kobo-specific sync protocol docs
- bruno/devices/koreader/api.yml: KOReader-specific sync protocol docs
- bruno/opds/*: Added OPDS feed and download endpoint documentation
- bruno/library/browse-folders.yml: Library folder browsing API docs

### New Bruno Tests
- bruno/media-items/Search All Libraries.yml: Test search without library filter
- bruno/media-items/Search Specific Library.yml: Test search with library filter
- bruno/media-items/Search Invalid Library ID.yml: Test error handling

## Documentation

- docs/developer/api/media-items/search_media_items.md: Updated with library_id parameter
- IMPLEMENTATION_COLLECTION_FIX.md: Comprehensive implementation guide with test scenarios

## Testing

### Integration Tests
- Library filter tests verify correct filtering across multiple libraries
- Invalid library_id tests ensure proper error handling
- WebSocket tests verify user-scoped broadcast behavior
- User A no longer receives User B's collection updates

### Manual Testing Scenarios
- Open collection in multiple tabs - updates propagate correctly
- Type in search box while another tab adds books - no disruptive reload
- Add/remove books from collection - toast notifications appear
- Toggle library filter - results update dynamically

## Technical Details

- WebSocket broadcasts are now user-scoped for privacy
- Active element detection uses tagName and contenteditable attributes
- Library ID validation uses UUID format checking
- Progressive enhancement maintained - page works without JavaScript
- All changes follow PROJECT_GUIDELINES.md conventions
- TypeScript only for frontend logic
- TailwindCSS only for styling
- Procedural programming style throughout

## Breaking Changes

None - all changes are additive and backward compatible.

internal/handlers/collections.go

@@ -330,7 +330,7 @@ func (h *CollectionHandler) AddBooks(c echo.Context) error {
 	}
 
 	if addedCount > 0 && h.connManager != nil {
-		h.connManager.Broadcast(wsync.BroadcastMessage{
+		h.connManager.BroadcastToUser(userUUID.String(), wsync.BroadcastMessage{
 			Type:      "collection_updated",
 			Timestamp: time.Now().Format(time.RFC3339),
 			Data: map[string]interface{}{
@@ -374,6 +374,9 @@ func (h *CollectionHandler) BulkRemoveBooks(c echo.Context) error {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid collection id"})
 	}
 
+	user := c.Get("user").(database.Users)
+	userUUID := uuid.UUID(user.ID.Bytes)
+
 	var req BulkRemoveBooksRequest
 	if err := c.Bind(&req); err != nil {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": "invalid request"})
@@ -398,7 +401,7 @@ func (h *CollectionHandler) BulkRemoveBooks(c echo.Context) error {
 	}
 
 	if removedCount > 0 && h.connManager != nil {
-		h.connManager.Broadcast(wsync.BroadcastMessage{
+		h.connManager.BroadcastToUser(userUUID.String(), wsync.BroadcastMessage{
 			Type:      "collection_updated",
 			Timestamp: time.Now().Format(time.RFC3339),
 			Data: map[string]interface{}{
@@ -753,6 +756,7 @@ func (h *CollectionHandler) compareValues(itemValue, operator, ruleValue string)
 // Bulk add books to multiple collections
 func (h *CollectionHandler) HandleBulkAddBooks(c echo.Context) error {
 	user := c.Get("user").(database.Users)
+	userUUID := uuid.UUID(user.ID.Bytes)
 
 	var req struct {
 		Operations []struct {
@@ -828,7 +832,7 @@ func (h *CollectionHandler) HandleBulkAddBooks(c echo.Context) error {
 	}
 
 	if successCount > 0 && h.connManager != nil {
-		h.connManager.Broadcast(wsync.BroadcastMessage{
+		h.connManager.BroadcastToUser(userUUID.String(), wsync.BroadcastMessage{
 			Type:      "collection_updated",
 			Timestamp: time.Now().Format(time.RFC3339),
 			Data: map[string]interface{}{