签到重试机制+超话选择持久化+healthcheck优化+JSON解码防护

frontend/app.py

@@ -105,6 +105,10 @@ def index():
         return redirect(url_for('dashboard'))
     return redirect(url_for('login'))
 
+@app.route('/health')
+def health():
+    return 'ok', 200
+
 @app.route('/register', methods=['GET', 'POST'])
 def register():
     if request.method == 'POST':