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/pages/Dashboard.tsx

@@ -1,9 +1,22 @@
 import { useAuthStore } from '../store/auth'
+import DashboardGrid from '../components/dashboard/DashboardGrid'
 import AdminDashboard from '../components/dashboard/AdminDashboard'
 import ClientDashboard from '../components/dashboard/ClientDashboard'
 
 export default function DashboardPage() {
   const user = useAuthStore((s) => s.user)
   const isPrivileged = user?.role === 'admin' || user?.role === 'project_manager'
-  return isPrivileged ? <AdminDashboard /> : <ClientDashboard />
+
+  return (
+    <div className="space-y-8">
+      {/* Configurable widget grid — visible to all roles */}
+      <div className="p-8 pb-0">
+        <h1 className="text-2xl font-bold text-content mb-6">Dashboard</h1>
+        <DashboardGrid />
+      </div>
+
+      {/* Role-based analytics section */}
+      {isPrivileged ? <AdminDashboard /> : <ClientDashboard />}
+    </div>
+  )
 }