feat(download): remote-download quotas per count and per volume

Two new group settings: aria2_task_limit caps a user's concurrent
active download tasks (counted at submission via the task list), and
aria2_max_file_size aborts a task once aria2 resolves a total size
over the cap. Both 0 = unlimited, exposed in the admin group editor.

Resolves #16

Authored By: TDvorak <info@tdvorak.dev>

frontend/public/locales/en-US/dashboard.json

@@ -1317,6 +1317,10 @@
     "aria2OptionsDes": "Extra parameters for downloaders (qBittorrent or Aria2), written in JSON key-value format, see the downloader official documentation for available parameters.",
     "aria2BatchSize": "Max batch size of remote download tasks",
     "aria2BatchSizeDes": "Max number for submitting batched remote download tasks, fill in 0 to indicate no limit.",
+      "aria2TaskLimit": "Max concurrent remote download tasks",
+      "aria2TaskLimitDes": "Max number of active remote download tasks per user (queued, running, or suspended). 0 = no limit.",
+      "aria2MaxFileSize": "Max size per download task (bytes)",
+      "aria2MaxFileSizeDes": "Remote download tasks whose resolved total size exceeds this are aborted. 0 = no limit.",
     "migratePolicy": "Relocate storage policy",
     "migratePolicyDes": "Whether the user creates a storage policy relocation task.",
     "advanceDelete": "Advanced file deletion options",

frontend/public/locales/zh-CN/dashboard.json

@@ -1317,6 +1317,10 @@
     "aria2OptionsDes": "qBittorrent 或 Aria2 下载器的任务额外配置参数，以 JSON 键值对格式书写，可用参数请查阅官方文档。",
     "aria2BatchSize": "批量离线下载最大数量",
     "aria2BatchSizeDes": "批量创建离线下载时的最大数量，填写为 0 表示不限制。",
+    "aria2TaskLimit": "最大并发离线下载任务数",
+    "aria2TaskLimitDes": "每个用户同时处于排队、下载或暂停状态的离线下载任务上限，填 0 表示不限制。",
+    "aria2MaxFileSize": "单个下载任务最大体积（字节）",
+    "aria2MaxFileSizeDes": "解析后的下载总大小超过此值的任务将被中止，填 0 表示不限制。",
     "migratePolicy": "存储策略转移",
     "migratePolicyDes": "是否用户创建存储策略转移任务。",
     "advanceDelete": "高级文件删除选项",

frontend/src/api/dashboard.ts

@@ -58,6 +58,8 @@ export interface GroupSetting {
   remote_download_options?: Record<string, any>;
   source_batch?: number;
   aria2_batch?: number;
+  aria2_task_limit?: number;
+  aria2_max_file_size?: number;
   max_walked_files?: number;
   trash_retention?: number;
   redirected_source?: boolean;

frontend/src/component/Admin/Group/EditGroup/FileManagementSection.tsx

@@ -132,6 +132,27 @@ const FileManagementSection = () => {
     [setGroup],
   );
 
+  const onAria2TaskLimitChange = useCallback(
+    (e: React.ChangeEvent<HTMLInputElement>) => {
+      setGroup((p: GroupEnt) => ({
+        ...p,
+        settings: { ...p.settings, aria2_task_limit: parseInt(e.target.value) ? parseInt(e.target.value) : undefined },
+      }));
+    },
+    [setGroup],
+  );
+
+  const onAria2MaxFileSizeChange = useCallback(
+    (e: React.ChangeEvent<HTMLInputElement>) => {
+      const bytes = parseInt(e.target.value);
+      setGroup((p: GroupEnt) => ({
+        ...p,
+        settings: { ...p.settings, aria2_max_file_size: bytes > 0 ? bytes : undefined },
+      }));
+    },
+    [setGroup],
+  );
+
   const onAllowAdvanceDeleteChange = useCallback(
     (e: React.ChangeEvent<HTMLInputElement>) => {
       setGroup((p: GroupEnt) => ({
@@ -322,6 +343,36 @@ const FileManagementSection = () => {
                     <NoMarginHelperText>{t("group.aria2BatchSizeDes")}</NoMarginHelperText>
                   </FormControl>
                 </SettingForm>
+                <SettingForm title={t("group.aria2TaskLimit")} lgWidth={5}>
+                  <FormControl fullWidth>
+                    <DenseFilledTextField
+                      slotProps={{
+                        htmlInput: {
+                          type: "number",
+                          min: 0,
+                        },
+                      }}
+                      value={values.settings?.aria2_task_limit ?? 0}
+                      onChange={onAria2TaskLimitChange}
+                    />
+                    <NoMarginHelperText>{t("group.aria2TaskLimitDes")}</NoMarginHelperText>
+                  </FormControl>
+                </SettingForm>
+                <SettingForm title={t("group.aria2MaxFileSize")} lgWidth={5}>
+                  <FormControl fullWidth>
+                    <DenseFilledTextField
+                      slotProps={{
+                        htmlInput: {
+                          type: "number",
+                          min: 0,
+                        },
+                      }}
+                      value={values.settings?.aria2_max_file_size ?? 0}
+                      onChange={onAria2MaxFileSizeChange}
+                    />
+                    <NoMarginHelperText>{t("group.aria2MaxFileSizeDes")}</NoMarginHelperText>
+                  </FormControl>
+                </SettingForm>
               </Stack>
             </Collapse>
             <SettingForm lgWidth={5}>

inventory/types/types.go

@@ -44,6 +44,10 @@ type (
 		RemoteDownloadOptions map[string]interface{} `json:"remote_download_options,omitempty"` // 离线下载用户组配置
 		SourceBatchSize       int                    `json:"source_batch,omitempty"`
 		Aria2BatchSize        int                    `json:"aria2_batch,omitempty"`
+		// Aria2TaskLimit caps concurrent active remote-download tasks per user.
+		Aria2TaskLimit int `json:"aria2_task_limit,omitempty"`
+		// Aria2MaxFileSize caps the total byte size of a single download task.
+		Aria2MaxFileSize int64 `json:"aria2_max_file_size,omitempty"`
 		MaxWalkedFiles        int                    `json:"max_walked_files,omitempty"`
 		TrashRetention        int                    `json:"trash_retention,omitempty"`
 		RedirectedSource      bool                   `json:"redirected_source,omitempty"`

pkg/filemanager/workflows/remote_download.go

@@ -366,6 +366,15 @@ func (m *RemoteDownloadTask) monitor(ctx context.Context, dep dependency.Dep) (t
 
 	if m.state.Status == nil || m.state.Status.Total != status.Total {
 		m.l.Info("download size changed, re-validate files.")
+		// Group per-task volume cap: abort once the resolved size exceeds it.
+		var maxSize int64
+		if u := inventory.UserFromContext(ctx); u != nil && u.Edges.Group != nil {
+			maxSize = u.Edges.Group.Settings.Aria2MaxFileSize
+		}
+		if maxSize > 0 && status.Total > maxSize {
+			m.state.Status = status
+			return task.StatusError, fmt.Errorf("download size %d exceeds group limit %d (%w)", status.Total, maxSize, queue.CriticalErr)
+		}
 		// First time to get status / total size changed, check user capacity
 		if err := m.validateFiles(ctx, dep, status); err != nil {
 			m.state.Status = status

service/explorer/workflows.go

@@ -124,6 +124,23 @@ func (service *DownloadWorkflowService) CreateDownloadTask(c *gin.Context) ([]*T
 		return nil, serializer.NewError(serializer.CodeBatchAria2Size, "", nil)
 	}
 
+	// Concurrent active-task quota for this user's group.
+	if taskLimit := user.Edges.Group.Settings.Aria2TaskLimit; taskLimit > 0 {
+		active, err := dep.TaskClient().List(c, &inventory.ListTaskArgs{
+			PaginationArgs: &inventory.PaginationArgs{PageSize: 1},
+			UserID:         user.ID,
+			Types:          []string{queue.RemoteDownloadTaskType},
+			Status:         []task.Status{task.StatusQueued, task.StatusProcessing, task.StatusSuspending},
+		})
+		if err != nil {
+			return nil, serializer.NewError(serializer.CodeDBError, "Failed to count download tasks", err)
+		}
+		if active.PaginationResults.TotalItems >= taskLimit {
+			return nil, serializer.NewError(serializer.CodeBatchAria2Size,
+				fmt.Sprintf("Concurrent download task limit reached (%d)", taskLimit), nil)
+		}
+	}
+
 	// Validate src file
 	if service.SrcFile != "" {
 		src, err := fs.NewUriFromString(service.SrcFile)