refactor(assets): extract scanner logic into service modules

- Create file_utils.py with shared file utilities:
  - get_mtime_ns() - extract mtime in nanoseconds from stat
  - get_size_and_mtime_ns() - get both size and mtime
  - verify_file_unchanged() - check file matches DB mtime/size
  - list_files_recursively() - recursive directory listing

- Create bulk_ingest.py for bulk operations:
  - BulkInsertResult dataclass
  - batch_insert_seed_assets() - batch insert with conflict handling
  - prune_orphaned_assets() - clean up orphaned assets

- Update scanner.py to use new service modules instead of
  calling database queries directly

- Update ingest.py to use shared get_size_and_mtime_ns()

- Export new functions from services/__init__.py

Amp-Thread-ID: https://ampcode.com/threads/T-019c2ae7-f701-716a-a0dd-1feb988732fb
Co-authored-by: Amp <amp@ampcode.com>

app/assets/database/queries/__init__.py

@@ -52,48 +52,48 @@ from app.assets.database.queries.tags import (
 )
 
 __all__ = [
-    "asset_exists_by_hash",
-    "get_asset_by_hash",
-    "upsert_asset",
-    "bulk_insert_assets",
-    "asset_info_exists_for_asset_id",
-    "get_asset_info_by_id",
-    "insert_asset_info",
-    "get_or_create_asset_info",
-    "update_asset_info_timestamps",
-    "list_asset_infos_page",
-    "fetch_asset_info_asset_and_tags",
-    "fetch_asset_info_and_asset",
-    "update_asset_info_access_time",
-    "update_asset_info_name",
-    "update_asset_info_updated_at",
-    "set_asset_info_metadata",
-    "delete_asset_info_by_id",
-    "set_asset_info_preview",
-    "bulk_insert_asset_infos_ignore_conflicts",
-    "get_asset_info_ids_by_ids",
-    "CacheStateRow",
-    "list_cache_states_by_asset_id",
-    "upsert_cache_state",
-    "delete_cache_states_outside_prefixes",
-    "get_orphaned_seed_asset_ids",
-    "delete_assets_by_ids",
-    "get_cache_states_for_prefixes",
-    "bulk_set_needs_verify",
-    "delete_cache_states_by_ids",
-    "delete_orphaned_seed_asset",
-    "bulk_insert_cache_states_ignore_conflicts",
-    "get_cache_states_by_paths_and_asset_ids",
-    "ensure_tags_exist",
-    "get_asset_tags",
-    "set_asset_info_tags",
-    "add_tags_to_asset_info",
-    "remove_tags_from_asset_info",
-    "add_missing_tag_for_asset_id",
-    "remove_missing_tag_for_asset_id",
-    "list_tags_with_usage",
-    "bulk_insert_tags_and_meta",
     "AddTagsDict",
+    "CacheStateRow",
     "RemoveTagsDict",
     "SetTagsDict",
+    "add_missing_tag_for_asset_id",
+    "add_tags_to_asset_info",
+    "asset_exists_by_hash",
+    "asset_info_exists_for_asset_id",
+    "bulk_insert_asset_infos_ignore_conflicts",
+    "bulk_insert_assets",
+    "bulk_insert_cache_states_ignore_conflicts",
+    "bulk_insert_tags_and_meta",
+    "bulk_set_needs_verify",
+    "delete_asset_info_by_id",
+    "delete_assets_by_ids",
+    "delete_cache_states_by_ids",
+    "delete_cache_states_outside_prefixes",
+    "delete_orphaned_seed_asset",
+    "ensure_tags_exist",
+    "fetch_asset_info_and_asset",
+    "fetch_asset_info_asset_and_tags",
+    "get_asset_by_hash",
+    "get_asset_info_by_id",
+    "get_asset_info_ids_by_ids",
+    "get_asset_tags",
+    "get_cache_states_by_paths_and_asset_ids",
+    "get_cache_states_for_prefixes",
+    "get_or_create_asset_info",
+    "get_orphaned_seed_asset_ids",
+    "insert_asset_info",
+    "list_asset_infos_page",
+    "list_cache_states_by_asset_id",
+    "list_tags_with_usage",
+    "remove_missing_tag_for_asset_id",
+    "remove_tags_from_asset_info",
+    "set_asset_info_metadata",
+    "set_asset_info_preview",
+    "set_asset_info_tags",
+    "update_asset_info_access_time",
+    "update_asset_info_name",
+    "update_asset_info_timestamps",
+    "update_asset_info_updated_at",
+    "upsert_asset",
+    "upsert_cache_state",
 ]