Refactor: move RescanService logic inline into SchedulerService

RescanService was thin wrapper. Its logic (rescan, auto-download, folder
scan, WebSocket broadcasts) moved into SchedulerService as private methods.
RescanService and its module deleted.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/server/services/scheduler/__init__.py

@@ -1,17 +1,11 @@
 """Scheduler services package.
 
-Contains scheduler orchestration and rescan coordination:
+Contains scheduler orchestration:
 
 - scheduler_service: Cron-based scheduler using APScheduler
 """
 from __future__ import annotations
 
-from src.server.services.rescan_service import (
-    RescanService,
-    get_rescan_service,
-    reset_rescan_service,
-)
-
 from src.server.services.scheduler.scheduler_service import (
     SchedulerService,
     SchedulerServiceError,
@@ -20,10 +14,6 @@ from src.server.services.scheduler.scheduler_service import (
 )
 
 __all__ = [
-    # RescanService
-    "RescanService",
-    "get_rescan_service",
-    "reset_rescan_service",
     # Scheduler
     "SchedulerService",
     "SchedulerServiceError",