feat: allow api_key query parameter for ChatGPT UI

ChatGPT UI lacks custom header support for MCP servers. Added
query parameter fallback (?api_key=) alongside Authorization
header to authenticate requests.

Updated tests to cover query param authentication.

src/aegis_gitea_mcp/server.py

@@ -74,6 +74,10 @@ async def authenticate_request(request: Request, call_next):
     auth_header = request.headers.get("authorization")
     api_key = auth_validator.extract_bearer_token(auth_header)
 
+    # Fallback: allow API key via query parameter (for ChatGPT UI without headers)
+    if not api_key:
+        api_key = request.query_params.get("api_key")
+
     # Validate API key
     is_valid, error_message = auth_validator.validate_api_key(api_key, client_ip, user_agent)
 
@@ -83,7 +87,10 @@ async def authenticate_request(request: Request, call_next):
             content={
                 "error": "Authentication failed",
                 "message": error_message,
-                "detail": "Please provide a valid API key in the Authorization header: Bearer <api-key>",
+                "detail": (
+                    "Provide a valid API key via Authorization header (Bearer <api-key>) "
+                    "or ?api_key=<api-key> query parameter"
+                ),
             },
         )