feat: SaaS onboarding, Stripe billing, MFA, SSO, passkeys, refresh tokens

Complete SaaS self-service onboarding sprint:

- Stripe-powered signup flow: pricing page → checkout → provisioning → activation
- Refresh token infrastructure: 1h access tokens + 30-day httpOnly cookie refresh
- TOTP MFA with QR setup, recovery codes, and login challenge flow
- Google + Azure AD SSO (conditional on env vars) with account linking
- WebAuthn passkey registration and passwordless login
- Guided onboarding checklist with server-side progress tracking
- Stubbed email service (console + DB logging, ready for real provider)
- Settings page with tabbed security settings (MFA, passkeys, linked accounts)
- Login page enhanced with MFA verification, SSO buttons, passkey login
- Database migration 015 with all new tables and columns
- Version bump to 2026.03.17

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

frontend/src/App.tsx

@@ -4,6 +4,7 @@ import { AppLayout } from './components/layout/AppLayout';
 import { LoginPage } from './pages/auth/LoginPage';
 import { RegisterPage } from './pages/auth/RegisterPage';
 import { SelectOrgPage } from './pages/auth/SelectOrgPage';
+import { ActivatePage } from './pages/auth/ActivatePage';
 import { DashboardPage } from './pages/dashboard/DashboardPage';
 import { AccountsPage } from './pages/accounts/AccountsPage';
 import { TransactionsPage } from './pages/transactions/TransactionsPage';
@@ -37,6 +38,9 @@ import { AssessmentScenariosPage } from './pages/board-planning/AssessmentScenar
 import { AssessmentScenarioDetailPage } from './pages/board-planning/AssessmentScenarioDetailPage';
 import { ScenarioComparisonPage } from './pages/board-planning/ScenarioComparisonPage';
 import { BudgetPlanningPage } from './pages/board-planning/BudgetPlanningPage';
+import { PricingPage } from './pages/pricing/PricingPage';
+import { OnboardingPage } from './pages/onboarding/OnboardingPage';
+import { OnboardingPendingPage } from './pages/onboarding/OnboardingPendingPage';
 
 function ProtectedRoute({ children }: { children: React.ReactNode }) {
   const token = useAuthStore((s) => s.token);
@@ -77,6 +81,12 @@ function AuthRoute({ children }: { children: React.ReactNode }) {
 export function App() {
   return (
     <Routes>
+      {/* Public routes (no auth required) */}
+      <Route path="/pricing" element={<PricingPage />} />
+      <Route path="/activate" element={<ActivatePage />} />
+      <Route path="/onboarding/pending" element={<OnboardingPendingPage />} />
+
+      {/* Auth routes (redirect if already logged in) */}
       <Route
         path="/login"
         element={
@@ -101,6 +111,18 @@ export function App() {
           </ProtectedRoute>
         }
       />
+
+      {/* Onboarding (requires auth but not org selection) */}
+      <Route
+        path="/onboarding"
+        element={
+          <ProtectedRoute>
+            <OnboardingPage />
+          </ProtectedRoute>
+        }
+      />
+
+      {/* Admin routes */}
       <Route
         path="/admin"
         element={
@@ -111,6 +133,8 @@ export function App() {
       >
         <Route index element={<AdminPage />} />
       </Route>
+
+      {/* Main app routes (require auth + org) */}
       <Route
         path="/*"
         element={