backend overhaul

auth.py

@@ -0,0 +1,13 @@
+#!/usr/bin/env python3
+"""Authentication helpers.
+
+Kept in its own module so both app.py (context processor) and routes/admin.py
+(route guards) can import is_admin() without circular imports.
+"""
+from __future__ import annotations
+
+from flask import session as flask_session
+
+
+def is_admin() -> bool:
+    return bool(flask_session.get("is_admin"))