feat: UX polish, localization, advert relocation, and map filter fixes

- i18n: translate connection screen + chat tab keys into 13 locales;
  add "Send my contact" (advert) strings in all locales
- feat: move self-advert from home header into composer "+" action menu
  (new lib/utils/advert_helper.dart, always shows Flood/Direct sheet)
- fix: hide-repeaters map toggle was bypassed in simple mode
- fix: simple mode map now shows only favourite chat contacts
- fix: wrap ListTiles in Material (contact_tile secondary actions,
  inferred contact group card) to satisfy Flutter ink assertions
- device-authoritative contact/channel sync and UX review fixes

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

lib/utils/toast_logger.dart

@@ -2,7 +2,13 @@ import 'package:flutter/material.dart';
 import 'package:provider/provider.dart';
 import '../providers/messages_provider.dart';
 
-/// Toast logger utility - replaces SnackBar with system messages in the channels tab
+/// Global messenger key wired to [MaterialApp.scaffoldMessengerKey] in main.dart
+/// so toasts can be shown even when the calling context has no Scaffold.
+final GlobalKey<ScaffoldMessengerState> rootScaffoldMessengerKey =
+    GlobalKey<ScaffoldMessengerState>();
+
+/// Toast logger utility - shows a floating SnackBar and records a system
+/// message in the channels tab history
 class ToastLogger {
   /// Log an info message
   static void info(BuildContext context, String message) {
@@ -24,14 +30,55 @@ class ToastLogger {
     _log(context, message, 'error');
   }
 
-  /// Internal method to log a system message
+  /// Internal method to show a snackbar and log a system message
   static void _log(BuildContext context, String message, String level) {
+    _showSnackBar(context, message, level);
+
+    // Keep recording as a system message (feeds history/stats)
     try {
       final messagesProvider = context.read<MessagesProvider>();
       messagesProvider.logSystemMessage(text: message, level: level);
     } catch (e) {
-      // Fallback to print if provider is not available
+      // Provider not available - snackbar above is still shown
       debugPrint('[$level] $message');
     }
   }
+
+  static void _showSnackBar(BuildContext context, String message, String level) {
+    final messenger =
+        rootScaffoldMessengerKey.currentState ??
+        ScaffoldMessenger.maybeOf(context);
+    if (messenger == null) {
+      debugPrint('[$level] $message');
+      return;
+    }
+
+    Color? backgroundColor;
+    switch (level) {
+      case 'error':
+        backgroundColor = context.mounted
+            ? Theme.of(context).colorScheme.error
+            : Colors.red;
+        break;
+      case 'warning':
+        backgroundColor = Colors.orange;
+        break;
+      case 'success':
+        backgroundColor = Colors.green;
+        break;
+      default:
+        backgroundColor = null; // default surface color
+    }
+
+    // Don't queue rapid toasts behind each other
+    messenger.hideCurrentSnackBar();
+    messenger.showSnackBar(
+      SnackBar(
+        content: Text(message),
+        behavior: SnackBarBehavior.floating,
+        backgroundColor: backgroundColor,
+        duration: Duration(seconds: level == 'error' ? 4 : 3),
+      ),
+    );
+  }
 }