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

src/server/services/scheduler/scheduler_service.py

@@ -268,6 +268,9 @@ class SchedulerService:
             "image_scan_after_rescan": (
                 self._config.image_scan_after_rescan if self._config else True
             ),
+            "folder_naming_after_nfo_scan": (
+                self._config.folder_naming_after_nfo_scan if self._config else True
+            ),
             "last_run": (
                 self._last_scan_time.isoformat()
                 if self._last_scan_time
@@ -404,7 +407,18 @@ class SchedulerService:
                     logger.error("NFO scan failed: %s", exc, exc_info=True)
                     await self._broadcast("nfo_scan_error", {"error": str(exc)})
 
-            # 3. Auto-download (if enabled)
+            # 3. Folder naming (if enabled, runs after NFO scan)
+            if self._config and self._config.folder_naming_after_nfo_scan:
+                if self._config.nfo_scan_after_rescan:
+                    # Only run if NFO scan was also enabled (depends on year in DB)
+                    try:
+                        naming_result = await self._run_folder_naming()
+                        await self._broadcast("folder_naming_completed", naming_result.to_dict())
+                    except Exception as exc:
+                        logger.error("Folder naming failed: %s", exc, exc_info=True)
+                        await self._broadcast("folder_naming_error", {"error": str(exc)})
+
+            # 4. Auto-download (if enabled)
             if self._config and self._config.auto_download_after_rescan:
                 try:
                     queued = await self._run_auto_download()
@@ -413,7 +427,7 @@ class SchedulerService:
                     logger.error("Auto-download failed: %s", exc, exc_info=True)
                     await self._broadcast("auto_download_error", {"error": str(exc)})
 
-            # 4. Image scan (if enabled)
+            # 5. Image scan (if enabled)
             if self._config and self._config.image_scan_after_rescan:
                 try:
                     image_result = await self._run_image_scan()
@@ -536,6 +550,13 @@ class SchedulerService:
         )
         return result
 
+    async def _run_folder_naming(self) -> Any:
+        """Run folder naming fix to add missing years to folder names."""
+        from src.server.services.folder_naming_service import get_folder_naming_service
+        service = get_folder_naming_service()
+        logger.info("Starting folder naming scan...")
+        return await service.run()
+
     async def _run_auto_download(self) -> int:
         """Queue and start downloads for all series with missing episodes."""
         from src.server.models.download import EpisodeIdentifier