Add Phase 3 remote read-only file operations

Introduce dedicated remote file facade for /Clients paths, add agent read/download endpoints, enable remote view/properties/download/image preview in the web UI, and keep remote write operations disabled.

webui/backend/app/api/routes_files.py

@@ -5,10 +5,11 @@ from fastapi.responses import StreamingResponse
 from starlette.background import BackgroundTask
 
 from backend.app.api.schemas import ArchivePrepareRequest, DeleteRequest, FileInfoResponse, MkdirRequest, MkdirResponse, RenameRequest, RenameResponse, SaveRequest, SaveResponse, TaskCreateResponse, TaskDetailResponse, UploadResponse, ViewResponse
-from backend.app.dependencies import get_archive_download_task_service, get_delete_task_service, get_file_ops_service
+from backend.app.dependencies import get_archive_download_task_service, get_delete_task_service, get_file_ops_service, get_remote_file_service
 from backend.app.services.archive_download_task_service import ArchiveDownloadTaskService
 from backend.app.services.delete_task_service import DeleteTaskService
 from backend.app.services.file_ops_service import FileOpsService
+from backend.app.services.remote_file_service import RemoteFileService
 
 router = APIRouter(prefix="/files")
 
@@ -54,7 +55,10 @@ async def view(
     path: str,
     for_edit: bool = False,
     service: FileOpsService = Depends(get_file_ops_service),
+    remote_service: RemoteFileService = Depends(get_remote_file_service),
 ) -> ViewResponse:
+    if remote_service.handles_path(path):
+        return remote_service.view(path=path, for_edit=for_edit)
     return service.view(path=path, for_edit=for_edit)
 
 
@@ -62,7 +66,10 @@ async def view(
 async def info(
     path: str,
     service: FileOpsService = Depends(get_file_ops_service),
+    remote_service: RemoteFileService = Depends(get_remote_file_service),
 ) -> FileInfoResponse:
+    if remote_service.handles_path(path):
+        return remote_service.info(path=path)
     return service.info(path=path)
 
 
@@ -70,8 +77,9 @@ async def info(
 async def download(
     path: list[str] = Query(...),
     service: FileOpsService = Depends(get_file_ops_service),
+    remote_service: RemoteFileService = Depends(get_remote_file_service),
 ) -> StreamingResponse:
-    prepared = service.prepare_download(paths=path)
+    prepared = remote_service.prepare_download(paths=path) if any(remote_service.handles_path(item) for item in path) else service.prepare_download(paths=path)
     response = StreamingResponse(
         prepared["content"],
         headers=prepared["headers"],
@@ -143,7 +151,15 @@ async def pdf(
 async def image(
     path: str,
     service: FileOpsService = Depends(get_file_ops_service),
+    remote_service: RemoteFileService = Depends(get_remote_file_service),
 ) -> StreamingResponse:
+    if remote_service.handles_path(path):
+        prepared = remote_service.prepare_image_stream(path=path)
+        return StreamingResponse(
+            prepared["content"],
+            headers=prepared["headers"],
+            media_type=prepared["content_type"],
+        )
     prepared = service.prepare_image_stream(path=path)
     return StreamingResponse(
         prepared["content"],