chore: import upstream snapshot with attribution

servers/fastapi/utils/internal_http.py

@@ -0,0 +1,16 @@
+from utils.simple_auth import (
+    SESSION_COOKIE_NAME,
+    create_session_token,
+    get_configured_auth_username,
+    get_internal_auth_headers,
+)
+
+
+def internal_request_headers() -> dict[str, str]:
+    """Headers for trusted loopback calls between FastAPI and Next.js."""
+    headers = dict(get_internal_auth_headers())
+    username = get_configured_auth_username()
+    if username and "Cookie" not in headers:
+        token = create_session_token(username)
+        headers["Cookie"] = f"{SESSION_COOKIE_NAME}={token}"
+    return headers