Add authentication features for admin access

- Introduce a new `auth` module with login, logout, and user verification endpoints for a single admin user.
- Update backend routes to require admin authentication for sensitive operations, enhancing security.
- Modify frontend components to include an authentication provider and gate, ensuring only authorized users can access the application.
- Implement a login page for admin access, improving user experience and security management.
- Update API request handling to redirect unauthorized users to the login page, ensuring proper access control.

backend/routes/model_registry.py

@@ -16,13 +16,18 @@ from schemas import (
     ModelResourceTestResult,
     ModelResourceUpsert,
 )
+from services.auth import require_admin
 from services.interface_catalog import validate_fields
 from services.masking import mask_secrets, merge_secrets
 from services.model_resource_tester import test_model_resource
 from sqlalchemy import delete, select, update
 from sqlalchemy.ext.asyncio import AsyncSession
 
-router = APIRouter(prefix="/api", tags=["model-registry"])
+router = APIRouter(
+    prefix="/api",
+    tags=["model-registry"],
+    dependencies=[Depends(require_admin)],
+)
 
 
 def _definition_dict(row: InterfaceDefinition) -> dict: