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/schemas.py

@@ -76,6 +76,34 @@ class TagUsage(NamedTuple):
     count: int
 
 
+@dataclass(frozen=True)
+class AssetSummaryData:
+    info: AssetInfoData
+    asset: AssetData | None
+    tags: list[str]
+
+
+@dataclass(frozen=True)
+class ListAssetsResult:
+    items: list[AssetSummaryData]
+    total: int
+
+
+@dataclass(frozen=True)
+class DownloadResolutionResult:
+    abs_path: str
+    content_type: str
+    download_name: str
+
+
+@dataclass(frozen=True)
+class UploadResult:
+    info: AssetInfoData
+    asset: AssetData
+    tags: list[str]
+    created_new: bool
+
+
 def extract_info_data(info: AssetInfo) -> AssetInfoData:
     return AssetInfoData(
         id=info.id,