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.

tests/test_server.py

@@ -116,6 +116,18 @@ def test_list_tools_with_valid_key(client, mock_env):
     assert "input_schema" in tool
 
 
+def test_list_tools_with_query_param(client):
+    """Test /mcp/tools with API key in query parameter."""
+    response = client.get(
+        f"/mcp/tools?api_key={'a' * 64}"
+    )
+    
+    assert response.status_code == 200
+    data = response.json()
+    assert "tools" in data
+    assert len(data["tools"]) > 0
+
+
 def test_list_tools_no_auth_when_disabled(client_no_auth):
     """Test that /mcp/tools works without auth when disabled."""
     response = client_no_auth.get("/mcp/tools")