fix(production-readiness): 3-batch production readiness cleanup — 12 tasks

Batch 1 — User-facing fixes:
- B1-1: Pipeline verified end-to-end (14 Rust commands, 8 frontend invoke, fully connected)
- B1-2: MessageSearch restored to ChatArea with search button in DeerFlow header
- B1-3: Viking cleanup — removed 5 orphan invokes (no Rust impl), added addWithMetadata + storeWithSummaries methods + summary generation UI
- B1-4: api-fallbacks transparency — added _isFallback markers + console.warn to all 6 fallback functions

Batch 2 — System health:
- B2-1: Document drift calibration — TRUTH.md/README.md numbers verified and updated
- B2-2: @reserved annotations on 15 SaaS handler functions with no frontend callers
- B2-3: Scheduled Task Admin V2 — new service + page + route + sidebar navigation
- B2-4: TRUTH.md Pipeline/Viking/ScheduledTask records corrected

Batch 3 — Long-term quality:
- B3-1: hand_run_status/hand_run_list verified as fully implemented (not stubs)
- B3-2: Identity snapshot rollback UI added to RightPanel
- B3-3: P2 code quality — 4 fixes (TODO comments, fire-and-forget notes, design notes, table name validation), 2 verified N/A, 1 upstream
- B3-4: Config PATCH→PUT alignment (admin-v2 config.ts matched to SaaS backend)

admin-v2/src/router/index.tsx

@@ -30,6 +30,7 @@ export const router = createBrowserRouter([
       { path: 'usage', lazy: () => import('@/pages/Usage').then((m) => ({ Component: m.default })) },
       { path: 'billing', lazy: () => import('@/pages/Billing').then((m) => ({ Component: m.default })) },
       { path: 'relay', lazy: () => import('@/pages/Relay').then((m) => ({ Component: m.default })) },
+      { path: 'scheduled-tasks', lazy: () => import('@/pages/ScheduledTasks').then((m) => ({ Component: m.default })) },
       { path: 'knowledge', lazy: () => import('@/pages/Knowledge').then((m) => ({ Component: m.default })) },
       { path: 'config', lazy: () => import('@/pages/Config').then((m) => ({ Component: m.default })) },
       { path: 'prompts', lazy: () => import('@/pages/Prompts').then((m) => ({ Component: m.default })) },