feat: implement AI model API proxy service

backend/app/middleware/auth.py

@@ -0,0 +1,53 @@
+"""Authentication middleware."""
+from typing import Optional
+from fastapi import Depends, HTTPException, status
+from fastapi.security import HTTPBearer, HTTPAuthorizationCredentials
+from ..models import ClientKey
+from ..services.auth import AuthService
+
+security = HTTPBearer(auto_error=False)
+
+
+async def get_current_client(
+    credentials: Optional[HTTPAuthorizationCredentials] = Depends(security)
+) -> ClientKey:
+    """Dependency to get and validate the current client.
+
+    Raises:
+        HTTPException: If authentication fails
+
+    Returns:
+        The validated ClientKey
+    """
+    if not credentials:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail={"error": "Missing API key"}
+        )
+
+    client_key = await AuthService.validate_key(credentials.credentials)
+
+    if not client_key:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail={"error": "Invalid API key"}
+        )
+
+    if not client_key.is_active:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail={"error": "API key disabled"}
+        )
+
+    return client_key
+
+
+class AuthMiddleware:
+    """Authentication middleware for request processing."""
+
+    def __init__(self, exclude_paths: list[str] = None):
+        self.exclude_paths = exclude_paths or ["/health", "/docs", "/openapi.json"]
+
+    async def __call__(self, request, call_next):
+        # Middleware is handled via Depends in routes
+        return await call_next(request)