docs: update comprehensive API documentation and project guides

This commit updates all documentation files throughout the project:

- Updated IMPLEMENTATION_PLAN.md with new implementation details
- Updated PROJECT_GUIDELINES.md with coding standards and practices
- Updated README.md with current project information
- Updated SCREENSHOT_AUTOMATION.md with new automation details
- Added TEST_DATA.md with test fixtures data
- Updated cover_image_serving_plan.md with static URL patterns

Documentation API updates:
- Updated API reference documentation for all endpoints including:
  - Authentication (login, logout, register, refresh_token)
  - Book matching (auto_link, bulk_link, link_book, search)
  - Collections (CRUD operations, shelf mappings, auto-assign rules)
  - Conflicts (bulk operations, resolve/dismiss)
  - Devices (registration, approval, shelf management)
  - Highlights (create, update, delete, get)
  - Kobo sync (bookmark, markup, initialization, sync)
  - KOReader sync (library, metadata, bookmarks, progress)
  - Libraries (CRUD, folders, media items, stats)
  - Media items (bulk operations, CRUD)
  - Notes (CRUD operations)
  - OPDS (acquisition, feeds, publication)
  - Progress (reading progress tracking)
  - Queue (device queue management)
  - Ratings (star ratings)
  - Scanner (watch mode, scan operations)
  - Sync protocols (Kobo, KOReader)
  - Users (profile, password, admin operations)
  - WebSocket protocols

- Updated user guides (admin, dashboard, settings, sync)
- Updated device setup guides (Kobo, KOReader)
- Updated developer guides (testing, contributing, operations)
- Updated scripts/README.md

docs/developer/testing.md

@@ -9,6 +9,7 @@ This document describes how to run and write tests for Bookhoard.
 All integration tests use the email domain **`@tests.bookhoard.internal`** for test users. This domain is reserved exclusively for testing and will never be used in production.
 
 **Why this domain?**
+
 - Clear indication it's for testing only
 - Won't conflict with real user emails (which use real domains like `@gmail.com`, `@example.com`, etc.)
 - Safe cleanup: Tests can delete all users with this domain without risk to production data
@@ -33,6 +34,7 @@ The test suite creates these standard users:
 ### Test Lifecycle and Cleanup
 
 Each test run:
+
 1. **Deletes** all existing users with `@tests.bookhoard.internal` email
 2. **Creates** fresh standard test users
 3. **Runs** the test with clean state
@@ -45,12 +47,14 @@ This ensures complete test isolation - no state leaks between tests.
 When writing new tests:
 
 **✅ DO:**
+
 - Use the standard test users from `setupTestServer(t)`
 - Use `createRegularUserOnce(t, setup.DB)` for additional test users
 - Let the test framework handle cleanup
 - Use the `@tests.bookhoard.internal` domain if creating custom test users
 
 **❌ DON'T:**
+
 - Use real email domains like `@example.com` or `@gmail.com`
 - Manually manage test user deletion (unless absolutely necessary)
 - Assume test users persist between test runs
@@ -59,21 +63,25 @@ When writing new tests:
 ## Running Tests
 
 ### Run All Tests
+
 ```bash
 make test
 ```
 
 ### Run Integration Tests Only
+
 ```bash
 make test-integration
 ```
 
 ### Run Specific Test
+
 ```bash
 go test -v -run TestUpdateProfile ./cmd/server/tests/
 ```
 
 ### Run with Race Detection
+
 ```bash
 go test -race ./cmd/server/tests/
 ```