Add Google Drive authorization processing and error handling templates

- Implemented `google_drive_callback.html` for processing Google Drive authorization, including UI for success and error states.
- Added JavaScript functionality for exchanging authorization codes, saving settings, and handling folder selection.
- Created `google_drive_callback_error.html` to display error messages during the authorization process.

app/api/__init__.py

@@ -13,6 +13,7 @@ from app.api.onedrive import router as onedrive_router
 from app.api.dropbox import router as dropbox_router
 from app.api.openai import router as openai_router
 from app.api.azure import router as azure_router
+from app.api.google_drive import router as google_drive_router
 
 # Set up logging
 logger = logging.getLogger(__name__)
@@ -29,3 +30,4 @@ router.include_router(onedrive_router)
 router.include_router(dropbox_router)
 router.include_router(openai_router)
 router.include_router(azure_router)
+router.include_router(google_drive_router)