scanner: fix library isolation, file mtime, force rescan, and deletion handling

Fix 1 - File modification time for created_at:
- Get file.ModTime() in processMediaFile and pass to CreateMediaItem
- Modified SQL INSERT to include created_at column

Fix 2 - Force rescan UPDATE instead of DELETE+INSERT:
- Changed force rescan logic to call updateMediaItem instead of delete + create
- Preserves created_at timestamp on force rescan

Fix 3 - GetMediaItemByFilePath filters by library_id:
- Added library_id to WHERE clause in SQL query
- Created GetMediaItemByFilePathAnyLibrary for cross-library lookups (KOReader)
- Added SetLibraryID method to MediaScanner
- Updated handler to call SetLibraryID for watch mode

Fix 4 - File deletion handling with persistent logging:
- Added fsnotify.Remove handler in WatchChanges
- Added orphan cleanup in ScanFolders after scan completes
- Created scanner_logger.go with daily log rotation (7 days)
- Logs to /app/logs/scanner-deletes-YYYY-MM-DD.log and scanner-errors-YYYY-MM-DD.log
- Individual deletes with enhanced safety logging

Note: Integration tests can now safely scan /app/uploads because
GetMediaItemByFilePath now filters by library_id, preventing
cross-library interference.

bruno/environments/Bookhoard.yml

@@ -13,9 +13,9 @@ variables:
   - name: note_id
     value: 7710a602-g29b-61d4-c716-446655440002
   - name: library_id
-    value: 551ac19c-896a-4406-b479-353fc489b295
+    value: 849151fb-564e-4b24-89e3-d11360789576
   - name: job_id
-    value: 450094c6-a8f1-4125-aea7-77df80223877
+    value: 295654b3-eb4b-4e85-ac6c-9361c5821195
   - name: rating
     value: "5"
   - name: is_visible
@@ -33,4 +33,4 @@ variables:
   - secret: true
     name: other_device_id
   - name: collection_id
-    value: 11e8d915-ef95-4257-98b3-b8eeacfd59b9
+    value: 412c03c3-0843-4bd4-b764-cc9457bb9df2