feat: implement AI model API proxy service

backend/app/models/provider_key.py

@@ -0,0 +1,13 @@
+"""Provider API Key model."""
+from dataclasses import dataclass
+from typing import Optional
+
+
+@dataclass
+class ProviderKey:
+    """API key for a provider."""
+    id: int
+    provider_id: int
+    key: str
+    is_active: bool
+    created_at: str