알림삭제 기능 추가

backend/src/main/java/com/goldenchart/service/TradeSignalService.java

@@ -69,6 +69,52 @@ public class TradeSignalService {
                 .stream().map(this::toDto).toList();
     }
 
+    // ── 삭제 ─────────────────────────────────────────────────────────────────
+
+    public void deleteOne(Long id, Long userId, String deviceId) {
+        if (id == null) return;
+        repo.findById(id).ifPresent(entity -> {
+            if (!owns(entity, userId, deviceId)) return;
+            repo.delete(entity);
+            log.info("[TradeSignal] deleted id={} market={}", id, entity.getMarket());
+        });
+    }
+
+    public int deleteBatch(List<Long> ids, Long userId, String deviceId) {
+        if (ids == null || ids.isEmpty()) return 0;
+        List<GcTradeSignal> toDelete = ids.stream()
+                .distinct()
+                .map(repo::findById)
+                .filter(java.util.Optional::isPresent)
+                .map(java.util.Optional::get)
+                .filter(e -> owns(e, userId, deviceId))
+                .toList();
+        if (toDelete.isEmpty()) return 0;
+        repo.deleteAll(toDelete);
+        log.info("[TradeSignal] batch deleted count={}", toDelete.size());
+        return toDelete.size();
+    }
+
+    public int deleteAll(Long userId, String deviceId) {
+        if (userId != null) {
+            long count = repo.findByUserIdOrderByCreatedAtDesc(userId).size();
+            repo.deleteByUserId(userId);
+            log.info("[TradeSignal] deleted all for userId={} count≈{}", userId, count);
+            return (int) count;
+        }
+        String dev = deviceId != null ? deviceId : "";
+        long count = repo.findByDeviceIdOrderByCreatedAtDesc(dev).size();
+        repo.deleteByDeviceId(dev);
+        log.info("[TradeSignal] deleted all for deviceId={} count≈{}", dev, count);
+        return (int) count;
+    }
+
+    private static boolean owns(GcTradeSignal entity, Long userId, String deviceId) {
+        if (userId != null && userId.equals(entity.getUserId())) return true;
+        if (deviceId == null || deviceId.isBlank()) return false;
+        return deviceId.equals(entity.getDeviceId());
+    }
+
     // ── 변환 ─────────────────────────────────────────────────────────────────
 
     private TradeSignalDto toDto(GcTradeSignal e) {