feat: add folder naming service to fix missing years in anime folder names

Runs after NFO refresh during scheduled rescans. Renames folders that
are missing a year (e.g. 'Naruto' → 'Naruto (1999)') using the year
from the database record.

Safety: _build_target_folder() always strips any existing year suffix
first, preventing double/triple year accumulation like
'Naruto (1999) (1999) (1999)'.

Changes:
- New FolderNamingService (folder_naming_service.py) with safe target
  name construction, DB update, and in-memory cache update
- New SchedulerConfig field: folder_naming_after_nfo_scan (default True)
- Integrated as step 3 in scheduler _perform_rescan() after NFO scan
- Runtime UI: existing 'folder-scan-enabled' checkbox in index.html
  now wired to toggle the feature (app.js + scheduler-config.js)
- Setup screen: new checkbox in setup.html Scheduler Settings section
- API: scheduler config endpoint returns all scan toggles
- Tests: 39 unit tests covering static helpers, rename logic, safety
  guard, and integration cases (folder_naming_service.py)
- Docs: testing guide updated with FolderNamingService examples

Docs/TESTING.md

@@ -1,104 +1,33 @@
-# Testing Documentation
 
-## Document Purpose
+### Testing FolderNamingService
 
-This document describes the testing strategy, guidelines, and practices for the Aniworld project.
-
-### What This Document Contains
-
--   **Testing Strategy**: Overall approach to quality assurance
--   **Test Categories**: Unit, integration, API, performance, security tests
--   **Test Structure**: Organization of test files and directories
--   **Writing Tests**: Guidelines for writing effective tests
--   **Fixtures and Mocking**: Shared test utilities and mock patterns
--   **Running Tests**: Commands and configurations
--   **Coverage Requirements**: Minimum coverage thresholds
--   **CI/CD Integration**: How tests run in automation
--   **Test Data Management**: Managing test fixtures and data
--   **Best Practices**: Do's and don'ts for testing
-
-### What This Document Does NOT Contain
-
--   Production deployment (see [DEPLOYMENT.md](DEPLOYMENT.md))
--   Security audit procedures (see [SECURITY.md](SECURITY.md))
--   Bug tracking and issue management
--   Performance benchmarking results
-
-### Target Audience
-
--   Developers writing tests
--   QA Engineers
--   CI/CD Engineers
--   Code reviewers
-
----
-
-## Sections to Document
-
-1. Testing Philosophy
-    - Test pyramid approach
-    - Quality gates
-2. Test Categories
-    - Unit Tests (`tests/unit/`)
-    - Integration Tests (`tests/integration/`)
-    - API Tests (`tests/api/`)
-    - Frontend Tests (`tests/frontend/`)
-    - Performance Tests (`tests/performance/`)
-    - Security Tests (`tests/security/`)
-3. Test Structure and Naming
-    - File naming conventions
-    - Test function naming
-    - Test class organization
-4. Running Tests
-    - pytest commands
-    - Running specific tests
-    - Verbose output
-    - Coverage reports
-5. Fixtures and Conftest
-    - Shared fixtures
-    - Database fixtures
-    - Mock services
-6. Mocking Guidelines
-    - What to mock
-    - Mock patterns
-    - External service mocks
-
-### Mocking the Download Queue
-
-Use `MockQueueRepository` for testing download queue functionality:
-
-```python
-from src.server.models.download import DownloadItem, EpisodeIdentifier
-
-class MockQueueRepository:
-    def __init__(self):
-        self._items: Dict[str, DownloadItem] = {}
-```
-
-### Testing SetupService
-
-SetupService handles series key resolution from folder names during library setup. Test file: `tests/unit/test_setup_service.py`.
+FolderNamingService fixes missing years in anime folder names after NFO refresh. Test file: `tests/unit/test_folder_naming_service.py`.
 
 Key methods tested:
+- `_build_target_folder()` — constructs safe "Title (YYYY)" names, strips existing year suffix first (prevents double-year like "Naruto (1999) (1999)")
+- `_folder_has_year()` — detects existing `(YYYY)` pattern
 - `_extract_year_from_folder_name()` — parses `(YYYY)` suffix
 - `_extract_title_from_folder_name()` — strips year suffix
-- `_resolve_key_via_search()` — resolves provider key via fuzzy title matching
 
 ```python
-@pytest.mark.asyncio
-async def test_returns_key_when_single_exact_match(self):
-    """Search returns 1 result with same name → returns key."""
-    mock_series_app = AsyncMock()
-    mock_series_app.search.return_value = [
-        {'title': 'Attack on Titan', 'link': '/anime/stream/attack-on-titan'}
-    ]
+# Safe: repeated calls never accumulate years
+r1 = FolderNamingService._build_target_folder("Naruto", 1999)
+r2 = FolderNamingService._build_target_folder(r1, 1999)
+assert r1 == r2 == "Naruto (1999)"
 
-    with patch('src.server.services.setup_service.get_series_app', return_value=mock_series_app):
-        result = await SetupService._resolve_key_via_search("Attack on Titan")
-
-    assert result == 'attack-on-titan'
+# Safe: existing year is replaced, not appended
+result = FolderNamingService._build_target_folder("Naruto (2020)", 1999)
+assert result == "Naruto (1999)"
+assert "2020" not in result
 ```
 
+The service is also tested end-to-end with mocked filesystem and database:
+- Renames folder and updates DB when year is missing from folder name
+- Skips rename when folder already has a year
+- Skips rename when DB has no year
+- Skips when target folder already exists on disk
+- Safety guard detects and skips if target folder year mismatches DB year
+
 ### Mocking aiohttp Sessions
 
 When testing code that uses `aiohttp.ClientSession`: