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/templates/setup.html

@@ -479,6 +479,13 @@
                                 <span>Auto-download missing episodes after rescan</span>
                             </label>
                         </div>
+                        <div class="form-group">
+                            <label class="form-checkbox">
+                                <input type="checkbox" id="scheduler_folder_naming" name="scheduler_folder_naming">
+                                <span>Fix missing years in folder names after NFO refresh</span>
+                            </label>
+                            <div class="form-help">Renames folders (e.g. "Naruto" → "Naruto (1999)") using the year from the database.</div>
+                        </div>
                     </div>
                 </div>
 
@@ -761,6 +768,7 @@
                 scheduler_schedule_time: document.getElementById('scheduler_schedule_time').value || '03:00',
                 scheduler_schedule_days: Array.from(document.querySelectorAll('.scheduler-day-setup-cb:checked')).map(cb => cb.value),
                 scheduler_auto_download_after_rescan: document.getElementById('scheduler_auto_download').checked,
+                scheduler_folder_naming_after_nfo_scan: document.getElementById('scheduler_folder_naming').checked,
                 logging_level: document.getElementById('logging_level').value,
                 logging_file: document.getElementById('logging_file').value.trim() || null,
                 logging_max_bytes: document.getElementById('logging_max_bytes').value ?