refactor: Projektstruktur in app/ und backend/ aufgeteilt

app/lib/widgets/offline_banner.dart

@@ -0,0 +1,168 @@
+import 'dart:async';
+import 'package:flutter/material.dart';
+import 'package:votianlt_app/services/developer.dart' as developer;
+import 'package:votianlt_app/services/websocket_service.dart';
+import 'package:votianlt_app/services/dart_mq.dart';
+
+class OfflineBanner extends StatefulWidget {
+  const OfflineBanner({super.key});
+
+  @override
+  State<OfflineBanner> createState() => _OfflineBannerState();
+}
+
+class _OfflineBannerState extends State<OfflineBanner> {
+  final StompService _stompService = StompService();
+  DartMQSubscription? _connSub;
+  Timer? _countdownTimer;
+  int _secondsToRetry = 15;
+  bool _hadConnection = false; // Track if we ever had a successful connection
+
+  @override
+  void initState() {
+    super.initState();
+    // Check if we're already connected (e.g., coming back to this screen)
+    _hadConnection = _stompService.isConnected && _stompService.isAuthenticated;
+    // Initialize countdown based on current connection state
+    _onConnectionChange(_stompService.isConnected && _stompService.isAuthenticated);
+    _connSub = DartMQ().subscribe<bool>(MQTopics.connectionStatus, _onConnectionChange);
+  }
+
+  void _onConnectionChange(bool isConnected) {
+    if (!mounted) return;
+    if (isConnected) {
+      _hadConnection = true; // Mark that we had a successful connection
+      _stopCountdown();
+      setState(() {});
+    } else {
+      _startCountdown();
+    }
+  }
+
+  void _startCountdown() {
+    _stopCountdown();
+    setState(() {
+      _secondsToRetry = 15;
+    });
+    _countdownTimer = Timer.periodic(const Duration(seconds: 1), (_) async {
+      if (!mounted) return;
+      if (_stompService.isConnected) {
+        _stopCountdown();
+        return;
+      }
+
+      // Decrement until 0, then attempt reconnect
+      if (_secondsToRetry > 1) {
+        setState(() {
+          _secondsToRetry = _secondsToRetry - 1;
+        });
+        return;
+      }
+
+      // Show 0 for one tick and try to reconnect now
+      setState(() {
+        _secondsToRetry = 0;
+      });
+
+      try {
+        // Only auto-reconnect if we already know the target; discovery remains user-initiated
+        await _stompService.connect();
+      } catch (e, stackTrace) {
+        developer.log('Auto-reconnect attempt failed: $e', name: 'OfflineBanner');
+        developer.log('Stack trace: $stackTrace', name: 'OfflineBanner');
+      }
+
+      if (!mounted) return;
+      if (!_stompService.isConnected) {
+        // Still offline -> reset countdown for next attempt
+        setState(() {
+          _secondsToRetry = 15;
+        });
+      }
+    });
+  }
+
+  void _stopCountdown() {
+    _countdownTimer?.cancel();
+    _countdownTimer = null;
+  }
+
+  @override
+  void dispose() {
+    _stopCountdown();
+    _connSub?.cancel();
+    _connSub = null;
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final isOnline = _stompService.isConnected && _stompService.isAuthenticated;
+    if (isOnline) return const SizedBox.shrink();
+
+    // Different messages for initial connection vs connection lost
+    final String title;
+    final String subtitle;
+    final IconData icon;
+    final Color? bgColor;
+    final Color? iconColor;
+    final Color? titleColor;
+    final Color? subtitleColor;
+
+    if (_hadConnection) {
+      // Connection was lost
+      title = 'Offline – Verbindung verloren';
+      subtitle = 'Verbindung wird wiederhergestellt.';
+      icon = Icons.wifi_off;
+      bgColor = Colors.red[50];
+      iconColor = Colors.red[700];
+      titleColor = Colors.red[900];
+      subtitleColor = Colors.red[800];
+    } else {
+      // Initial connection attempt
+      title = 'Verbinde mit Server...';
+      subtitle = 'Bitte warten.';
+      icon = Icons.sync;
+      bgColor = Colors.orange[50];
+      iconColor = Colors.orange[700];
+      titleColor = Colors.orange[900];
+      subtitleColor = Colors.orange[800];
+    }
+
+    return Container(
+      width: double.infinity,
+      padding: const EdgeInsets.symmetric(vertical: 10, horizontal: 12),
+      color: bgColor,
+      child: Row(
+        children: [
+          Icon(icon, color: iconColor),
+          const SizedBox(width: 8),
+          Expanded(
+            child: Column(
+              crossAxisAlignment: CrossAxisAlignment.start,
+              mainAxisSize: MainAxisSize.min,
+              children: [
+                Text(
+                  title,
+                  style: TextStyle(
+                    color: titleColor,
+                    fontWeight: FontWeight.w700,
+                  ),
+                ),
+                const SizedBox(height: 2),
+                Text(
+                  subtitle,
+                  style: TextStyle(
+                    color: subtitleColor,
+                    fontSize: 12,
+                  ),
+                ),
+              ],
+            ),
+          ),
+        ],
+      ),
+    );
+  }
+}
+