add support for badges and notifications, adjust nav pages

lib/services/data_service/data_service_badges.dart

@@ -0,0 +1,42 @@
+part of 'data_service.dart';
+
+extension DataServiceBadges on DataService {
+  Future<void> fetchBadgeAwards() async {
+    _isBadgeAwardsLoading = true;
+    try {
+      final json = await api.get('/badge/awards/me');
+      List<dynamic>? list;
+      if (json is List) {
+        list = json;
+      } else if (json is Map) {
+        for (final key in ['awards', 'badge_awards', 'data']) {
+          final value = json[key];
+          if (value is List) {
+            list = value;
+            break;
+          }
+        }
+      }
+      final parsed = list
+          ?.whereType<Map<String, dynamic>>()
+          .map(BadgeAward.fromJson)
+          .toList();
+      if (parsed != null) {
+        parsed.sort((a, b) {
+          final aTs = a.awardedAt?.millisecondsSinceEpoch ?? 0;
+          final bTs = b.awardedAt?.millisecondsSinceEpoch ?? 0;
+          return bTs.compareTo(aTs);
+        });
+        _badgeAwards = parsed;
+      } else {
+        _badgeAwards = [];
+      }
+    } catch (e) {
+      debugPrint('Failed to fetch badge awards: $e');
+      _badgeAwards = [];
+    } finally {
+      _isBadgeAwardsLoading = false;
+      _notifyAsync();
+    }
+  }
+}