feat(server): implement chat file TTL cleanup and enhance JPush vendor channel support

Add FileCleanupWorker for automatic expiration of chat files with configurable retention period and batch processing. Files uploaded via `/api/v1/uploads/files` are tracked in `uploaded_files` table with expiration timestamps, then deleted from S3 and database upon expiry. Expired file URLs are injected as `"expired": true` in message responses.

Extend JPush push notification configuration with vendor-specific channel_id support (xiaomi, huawei, oppo, vivo, meizu, honor, fcm) for differentiating system vs chat notifications. Add iOS APNs thread-id grouping configuration for notification categorization.

internal/database/database.go

@@ -231,6 +231,9 @@ func autoMigrate(db *gorm.DB) error {
 		&model.TradeItem{},
 		&model.TradeImage{},
 		&model.TradeFavorite{},
+
+		// 文件上传记录（用于聊天文件 TTL 过期清理）
+		&model.UploadedFile{},
 	)
 	if err != nil {
 		return err