Refactor: Replace CallbackManager with Events pattern

- Replace callback system with events library in SerieScanner
- Update SeriesApp to subscribe to loader and scanner events
- Refactor ScanService to use Events instead of CallbackManager
- Remove CallbackManager imports and callback classes
- Add safe event calling with error handling in SerieScanner
- Update AniworldLoader to use Events for download progress
- Remove progress_callback parameter from download methods
- Update all affected tests for Events pattern
- Fix test_series_app.py for new event subscription model
- Comment out obsolete callback tests in test_scan_service.py

All core tests passing. Events provide cleaner event-driven architecture.

tests/unit/test_scan_service.py

@@ -1,29 +1,17 @@
 """Unit tests for ScanService.
 
 This module contains comprehensive tests for the scan service,
-including scan lifecycle, progress callbacks, event handling,
-and key-based identification.
+including scan lifecycle, progress events, and key-based identification.
 """
 from datetime import datetime
-from unittest.mock import AsyncMock, MagicMock
+from unittest.mock import AsyncMock, MagicMock, Mock
 
 import pytest
 
-from src.core.interfaces.callbacks import (
-    CallbackManager,
-    CompletionContext,
-    ErrorContext,
-    OperationType,
-    ProgressContext,
-    ProgressPhase,
-)
 from src.server.services.scan_service import (
     ScanProgress,
     ScanService,
-    ScanServiceCompletionCallback,
     ScanServiceError,
-    ScanServiceErrorCallback,
-    ScanServiceProgressCallback,
     get_scan_service,
     reset_scan_service,
 )