fix(notification): harden local alerts

lib/core/services/notification_service.dart

@@ -117,11 +117,15 @@ class NotificationService {
       enableVibration: true,
     );
 
-    await _notifications
-        .resolvePlatformSpecificImplementation<
-          AndroidFlutterLocalNotificationsPlugin
-        >()
-        ?.createNotificationChannel(androidChannel);
+    try {
+      await _notifications
+          .resolvePlatformSpecificImplementation<
+            AndroidFlutterLocalNotificationsPlugin
+          >()
+          ?.createNotificationChannel(androidChannel);
+    } catch (e) {
+      AppLogger.debug('안드로이드 채널 생성 실패: $e');
+    }
   }
 
   /// 알림 권한 요청
@@ -214,6 +218,46 @@ class NotificationService {
     return true;
   }
 
+  /// 정확 알람 권한 가능 여부 확인 (Android 12+)
+  Future<bool> canScheduleExactAlarms() async {
+    if (kIsWeb || defaultTargetPlatform != TargetPlatform.android) {
+      return true;
+    }
+
+    try {
+      final androidImplementation = _notifications
+          .resolvePlatformSpecificImplementation<
+            AndroidFlutterLocalNotificationsPlugin
+          >();
+      final canExact = await androidImplementation
+          ?.canScheduleExactNotifications();
+      return canExact ?? true;
+    } catch (e) {
+      AppLogger.debug('정확 알람 권한 확인 실패: $e');
+      return false;
+    }
+  }
+
+  /// 정확 알람 권한 요청 (Android 12+ 설정 화면 이동)
+  Future<bool> requestExactAlarmsPermission() async {
+    if (kIsWeb || defaultTargetPlatform != TargetPlatform.android) {
+      return true;
+    }
+
+    try {
+      final androidImplementation = _notifications
+          .resolvePlatformSpecificImplementation<
+            AndroidFlutterLocalNotificationsPlugin
+          >();
+      final granted = await androidImplementation
+          ?.requestExactAlarmsPermission();
+      return granted ?? false;
+    } catch (e) {
+      AppLogger.debug('정확 알람 권한 요청 실패: $e');
+      return false;
+    }
+  }
+
   // 알림 탭 콜백
   static void Function(NotificationResponse)? onNotificationTap;
 
@@ -238,7 +282,7 @@ class NotificationService {
       }
 
       final location = await _ensureLocalTimezone();
-      final minutesToWait = delayMinutes ?? 90 + Random().nextInt(31);
+      final minutesToWait = max(delayMinutes ?? 90 + Random().nextInt(31), 1);
       final scheduledTime = tz.TZDateTime.now(
         location,
       ).add(Duration(minutes: minutesToWait));
@@ -343,17 +387,9 @@ class NotificationService {
       return AndroidScheduleMode.exactAllowWhileIdle;
     }
 
-    try {
-      final androidImplementation = _notifications
-          .resolvePlatformSpecificImplementation<
-            AndroidFlutterLocalNotificationsPlugin
-          >();
-      final canExact = await androidImplementation
-          ?.canScheduleExactNotifications();
-      if (canExact == false) {
-        return AndroidScheduleMode.inexactAllowWhileIdle;
-      }
-    } catch (_) {
+    final canExact = await canScheduleExactAlarms();
+    if (!canExact) {
+      AppLogger.debug('정확 알람 권한 없음 → 근사 모드로 예약');
       return AndroidScheduleMode.inexactAllowWhileIdle;
     }