feat(upstreams): add batch test-all / check-now-all endpoints

- POST /api/upstreams/test-all: batch connection test for all enabled
  upstreams (no snapshot, no webhook); updates last_status, balance
- POST /api/upstreams/check-now-all: full batch sync (snapshot, diff,
  webhook, key sync, priority sync); mirrors single check-now behavior
- Both routes are registered before /{uid} to avoid path capture
- Skips disabled upstreams (status=skipped); single failure does not
  abort subsequent upstreams (serial execution)
- Returns UpstreamBatchActionResponse with per-item detail and summary

Refactor: extract _test_upstream_core(db, u) and _check_now_core(db, u)
- All four routes (single + batch × 2) now share the same core helpers
- Eliminates duplicate logic and future divergence risk

Frontend:
- Add UpstreamBatchActionResponse / Item / Summary TS types
- Add upstreamsApi.testAll() and upstreamsApi.checkNowAll()
- Add '一键测试' and '一键同步' buttons in Upstreams.vue toolbar
  (order: 一键测试 → 一键同步 → 刷新 → 新增上游)
- Buttons disabled when list is empty or another batch op is running
- On completion: refresh list + ElMessageBox with per-item failure detail

frontend/src/api/index.ts

@@ -139,6 +139,28 @@ export interface GenerateKeysByGroupsForm {
   endpoint: string
 }
 
+export interface UpstreamBatchActionItem {
+  upstream_id: number
+  upstream_name: string
+  status: 'success' | 'failed' | 'skipped'
+  message: string
+  detail?: string | null
+}
+
+export interface UpstreamBatchActionSummary {
+  total: number
+  success: number
+  failed: number
+  skipped: number
+}
+
+export interface UpstreamBatchActionResponse {
+  success: boolean
+  message: string
+  summary: UpstreamBatchActionSummary
+  items: UpstreamBatchActionItem[]
+}
+
 export const upstreamsApi = {
   list: () => api.get<UpstreamData[]>('/api/upstreams'),
   create: (data: UpstreamForm) => api.post<UpstreamData>('/api/upstreams', data),
@@ -152,6 +174,8 @@ export const upstreamsApi = {
   latestSnapshot: (id: number) => api.get(`/api/upstreams/${id}/snapshots/latest`),
   listSnapshots: (id: number, limit = 20, offset = 0) =>
     api.get<any[]>(`/api/upstreams/${id}/snapshots`, { params: { limit, offset } }),
+  testAll: () => api.post<UpstreamBatchActionResponse>('/api/upstreams/test-all'),
+  checkNowAll: () => api.post<UpstreamBatchActionResponse>('/api/upstreams/check-now-all'),
 }
 
 // ——— Websites ———