refactor: eliminate manager layer, routes call services directly

- Delete app/assets/manager.py
- Move upload logic (upload_from_temp_path, create_from_hash) to ingest service
- Add HashMismatchError and DependencyMissingError to ingest service
- Add UploadResult schema for upload responses
- Update routes.py to import services directly and do schema conversion inline
- Add asset lookup/listing service functions to asset_management.py

Routes now call the service layer directly, removing an unnecessary
layer of indirection. The manager was only converting between service
dataclasses and Pydantic response schemas.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

app/assets/services/__init__.py

@@ -1,23 +1,36 @@
 from app.assets.services.asset_management import (
+    asset_exists,
     delete_asset_reference,
+    get_asset_by_hash,
     get_asset_detail,
+    get_asset_info_with_tags,
+    list_assets_page,
+    resolve_asset_for_download,
     set_asset_preview,
     update_asset_metadata,
 )
 from app.assets.services.ingest import (
+    DependencyMissingError,
+    HashMismatchError,
+    create_from_hash,
     ingest_file_from_path,
     register_existing_asset,
+    upload_from_temp_path,
 )
 from app.assets.services.schemas import (
     AddTagsResult,
     AssetData,
     AssetDetailResult,
     AssetInfoData,
+    AssetSummaryData,
+    DownloadResolutionResult,
     IngestResult,
+    ListAssetsResult,
     RegisterAssetResult,
     RemoveTagsResult,
     SetTagsResult,
     TagUsage,
+    UploadResult,
     UserMetadata,
 )
 from app.assets.services.tagging import (
@@ -29,7 +42,16 @@ from app.assets.services.tagging import (
 __all__ = [
     "ingest_file_from_path",
     "register_existing_asset",
+    "upload_from_temp_path",
+    "create_from_hash",
+    "HashMismatchError",
+    "DependencyMissingError",
+    "asset_exists",
+    "get_asset_by_hash",
     "get_asset_detail",
+    "get_asset_info_with_tags",
+    "list_assets_page",
+    "resolve_asset_for_download",
     "update_asset_metadata",
     "delete_asset_reference",
     "set_asset_preview",
@@ -40,10 +62,14 @@ __all__ = [
     "AssetData",
     "AssetDetailResult",
     "AssetInfoData",
+    "AssetSummaryData",
+    "DownloadResolutionResult",
     "IngestResult",
+    "ListAssetsResult",
     "RegisterAssetResult",
     "RemoveTagsResult",
     "SetTagsResult",
     "TagUsage",
+    "UploadResult",
     "UserMetadata",
 ]