feat: implement AI model API proxy service

backend/app/services/auth.py

@@ -0,0 +1,36 @@
+"""Authentication service."""
+import aiosqlite
+from typing import Optional
+from ..database import db_connection
+from ..models import ClientKey
+
+
+class AuthService:
+    """Service for client key authentication."""
+
+    @staticmethod
+    async def validate_key(api_key: str) -> Optional[ClientKey]:
+        """Validate a client API key.
+
+        Args:
+            api_key: The API key to validate
+
+        Returns:
+            ClientKey if valid and active, None otherwise
+        """
+        async with db_connection() as db:
+            cursor = await db.execute(
+                """SELECT id, key, name, is_active, created_at
+                   FROM client_keys WHERE key = ?""",
+                (api_key,)
+            )
+            row = await cursor.fetchone()
+            if row and row["is_active"]:
+                return ClientKey(
+                    id=row["id"],
+                    key=row["key"],
+                    name=row["name"],
+                    is_active=row["is_active"],
+                    created_at=row["created_at"]
+                )
+            return None