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/handler/upload_handler.go

@@ -92,3 +92,39 @@ func (h *UploadHandler) UploadCover(c *gin.Context) {
 
 	response.Success(c, gin.H{"url": url})
 }
+
+// UploadFile 上传聊天/通用文件（非图片类资源）
+// form 字段：file（必填）、folder（可选，默认 chat）
+func (h *UploadHandler) UploadFile(c *gin.Context) {
+	userID := c.GetString("user_id")
+	if userID == "" {
+		response.Unauthorized(c, "")
+		return
+	}
+
+	file, err := c.FormFile("file")
+	if err != nil {
+		response.BadRequest(c, "file is required")
+		return
+	}
+
+	folder := c.DefaultPostForm("folder", "chat")
+
+	result, err := h.uploadService.UploadFile(c.Request.Context(), file, folder, userID)
+	if err != nil {
+		// 参数类错误（大小/类型）返回 400，其余返回 500
+		if file.Size > 0 && file.Size <= 100<<20 {
+			response.BadRequest(c, err.Error())
+			return
+		}
+		response.InternalServerError(c, "failed to upload file")
+		return
+	}
+
+	response.Success(c, gin.H{
+		"url":       result.URL,
+		"name":      result.Name,
+		"size":      result.Size,
+		"mime_type": result.MimeType,
+	})
+}