feat(L+M): configurable dashboard widget system + test framework

Phase L: Dashboard widget system
- Migration 046: dashboard_configs table (user/tenant/role fallback cascade)
- DashboardConfig model + dashboard_service with get/upsert per-user and tenant-default
- API router: GET/PUT /api/dashboard/config, GET/PUT /api/dashboard/tenant-default
- Frontend: 5 widget components (ProductionStats, QueueStatus, RecentRenders, CostOverview, WorkerStatus)
- DashboardGrid with API-backed config, DashboardCustomizeModal (checkbox selection, save/cancel)
- Dashboard.tsx: widget grid + analytics section (privileged users)
- Admin.tsx: restructured with new section order and Maintenance 2-col grid

Phase M: Test framework
- Backend: pytest-asyncio + pytest-cov + factory-boy in pyproject.toml
- conftest.py: excel_dir fixtures + async DB fixtures + mock storage/celery stubs
- Domain tests: billing_service, cache_service, notifications_service, imports_sanity
- Integration: test_api_health.py smoke test (requires running backend)
- Frontend: vitest + @testing-library/react + msw added to package.json
- vite.config.ts: test block (jsdom + globals + setupFiles)
- tsconfig.json: exclude src/__tests__ from main tsc (test runner handles its own types)
- MSW handlers for /api/auth/me, Billing.test.tsx, formatters.test.ts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/api/dashboard.ts

@@ -0,0 +1,56 @@
+import api from './client'
+
+export type WidgetType =
+  | 'ProductionStats'
+  | 'QueueStatus'
+  | 'RecentRenders'
+  | 'CostOverview'
+  | 'WorkerStatus'
+
+export interface WidgetPosition {
+  col: number
+  row: number
+  w: number
+  h: number
+}
+
+export interface WidgetConfig {
+  widget_type: WidgetType
+  position: WidgetPosition
+  config?: Record<string, unknown>
+}
+
+interface DashboardConfigResponse {
+  widgets: WidgetConfig[]
+}
+
+export async function getDashboardConfig(): Promise<WidgetConfig[]> {
+  const { data } = await api.get<DashboardConfigResponse>('/dashboard/config')
+  return data.widgets
+}
+
+export async function updateDashboardConfig(
+  widgets: WidgetConfig[]
+): Promise<WidgetConfig[]> {
+  const { data } = await api.put<DashboardConfigResponse>('/dashboard/config', {
+    widgets,
+  })
+  return data.widgets
+}
+
+export async function getTenantDefaultDashboard(): Promise<WidgetConfig[]> {
+  const { data } = await api.get<DashboardConfigResponse>(
+    '/dashboard/tenant-default'
+  )
+  return data.widgets
+}
+
+export async function updateTenantDefaultDashboard(
+  widgets: WidgetConfig[]
+): Promise<WidgetConfig[]> {
+  const { data } = await api.put<DashboardConfigResponse>(
+    '/dashboard/tenant-default',
+    { widgets }
+  )
+  return data.widgets
+}