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/web/static/js/index/scheduler-config.js

@@ -35,6 +35,11 @@ AniWorld.SchedulerConfig = (function() {
                     autoDownload.checked = config.auto_download_after_rescan || false;
                 }
 
+                const folderNaming = document.getElementById('folder-scan-enabled');
+                if (folderNaming) {
+                    folderNaming.checked = config.folder_naming_after_nfo_scan || false;
+                }
+
                 // Update schedule day checkboxes
                 const days = config.schedule_days || ['mon','tue','wed','thu','fri','sat','sun'];
                 ['mon','tue','wed','thu','fri','sat','sun'].forEach(function(day) {
@@ -87,7 +92,8 @@ AniWorld.SchedulerConfig = (function() {
                 enabled: enabled,
                 schedule_time: scheduleTime,
                 schedule_days: scheduleDays,
-                auto_download_after_rescan: autoDownload
+                auto_download_after_rescan: autoDownload,
+                folder_naming_after_nfo_scan: document.getElementById('folder-scan-enabled') ? document.getElementById('folder-scan-enabled').checked : false
             };
 
             const response = await AniWorld.ApiClient.post(API.SCHEDULER_CONFIG, payload);