feat: 添加多维度计费系统和视频任务管理功能

计费系统:
- 新增 BillingRule 和 DimensionCollector 数据模型
- 实现 FormulaEngine 安全表达式求值引擎 (AST 白名单)
- 支持 dimension/matrix/tiered/constant 多种维度映射
- BillingRuleService 支持 Provider Model -> GlobalModel 规则回退
- CLI task_type 在计费域自动映射为 chat

视频任务增强:
- 添加 request_metadata 字段记录候选 key 和计费规则快照
- 后台轮询支持并发控制 (Semaphore + 独立 session)
- 任务终态自动写入 Usage 记录并计算成本
- 新增视频任务管理 API 和前端界面

其他改进:
- UsageService 新增 record_usage_with_custom_cost 方法
- StandardizedUsage 支持 dimensions 字段 (兼容 extra)
- 配置新增 BILLING_REQUIRE_RULE 和 BILLING_STRICT_MODE

frontend/src/api/video-tasks.ts

@@ -0,0 +1,158 @@
+import apiClient from './client'
+
+// 视频任务状态
+export type VideoTaskStatus = 'pending' | 'submitted' | 'queued' | 'processing' | 'completed' | 'failed' | 'cancelled'
+
+// 视频任务列表项
+export interface VideoTaskItem {
+  id: string
+  external_task_id: string
+  user_id: string
+  username: string
+  model: string
+  prompt: string
+  status: VideoTaskStatus
+  progress_percent: number
+  progress_message: string | null
+  provider_id: string
+  provider_name: string
+  duration_seconds: number
+  resolution: string
+  aspect_ratio: string
+  video_url: string | null
+  error_code: string | null
+  error_message: string | null
+  poll_count: number
+  max_poll_count: number
+  created_at: string
+  completed_at: string | null
+  submitted_at: string | null
+}
+
+// 候选 Key 信息
+export interface CandidateKeyInfo {
+  index: number
+  provider_id: string
+  provider_name: string
+  endpoint_id: string
+  key_id: string
+  key_name: string | null
+  auth_type: string
+  has_billing_rule: boolean
+  priority: number
+  selected?: boolean
+}
+
+// 请求元数据
+export interface VideoTaskRequestMetadata {
+  candidate_keys: CandidateKeyInfo[]
+  selected_key_id: string
+  selected_endpoint_id: string
+  client_ip: string
+  user_agent: string
+  request_id: string
+  request_headers?: Record<string, string>
+}
+
+// 视频任务详情
+export interface VideoTaskDetail extends VideoTaskItem {
+  api_key_id: string
+  endpoint_id: string
+  key_id: string
+  client_api_format: string
+  provider_api_format: string
+  format_converted: boolean
+  original_request_body: any
+  converted_request_body: any
+  size: string | null
+  video_urls: string[] | null
+  thumbnail_url: string | null
+  video_size_bytes: number | null
+  video_expires_at: string | null
+  stored_video_path: string | null
+  storage_provider: string | null
+  retry_count: number
+  max_retries: number
+  poll_interval_seconds: number
+  next_poll_at: string | null
+  updated_at: string | null
+  endpoint: {
+    id: string
+    base_url: string
+    api_format: string
+  } | null
+  request_metadata: VideoTaskRequestMetadata | null
+}
+
+// 视频任务列表响应
+export interface VideoTaskListResponse {
+  items: VideoTaskItem[]
+  total: number
+  page: number
+  page_size: number
+  pages: number
+}
+
+// 视频任务统计响应
+export interface VideoTaskStatsResponse {
+  total: number
+  by_status: Record<VideoTaskStatus, number>
+  by_model: Record<string, number>
+  today_count: number
+  active_users?: number  // 仅管理员
+  processing_count?: number  // 仅管理员
+}
+
+// 视频任务查询参数
+export interface VideoTaskQueryParams {
+  status?: VideoTaskStatus
+  user_id?: string
+  model?: string
+  page?: number
+  page_size?: number
+}
+
+export const videoTasksApi = {
+  /**
+   * 获取视频任务列表
+   */
+  async list(params: VideoTaskQueryParams = {}): Promise<VideoTaskListResponse> {
+    const searchParams = new URLSearchParams()
+    if (params.status) searchParams.append('status', params.status)
+    if (params.user_id) searchParams.append('user_id', params.user_id)
+    if (params.model) searchParams.append('model', params.model)
+    if (params.page) searchParams.append('page', params.page.toString())
+    if (params.page_size) searchParams.append('page_size', params.page_size.toString())
+
+    const query = searchParams.toString()
+    const url = query ? `/api/admin/video-tasks?${query}` : '/api/admin/video-tasks'
+    const response = await apiClient.get(url)
+    return response.data
+  },
+
+  /**
+   * 获取视频任务统计
+   */
+  async getStats(): Promise<VideoTaskStatsResponse> {
+    const response = await apiClient.get('/api/admin/video-tasks/stats')
+    return response.data
+  },
+
+  /**
+   * 获取视频任务详情
+   */
+  async getDetail(taskId: string): Promise<VideoTaskDetail> {
+    const response = await apiClient.get(`/api/admin/video-tasks/${taskId}`)
+    return response.data
+  },
+
+  /**
+   * 取消视频任务
+   */
+  async cancel(taskId: string): Promise<{ id: string; status: string; message: string }> {
+    const response = await apiClient.post(`/api/admin/video-tasks/${taskId}/cancel`)
+    return response.data
+  },
+}
+
+export default videoTasksApi