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>

backend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "hoa-ledgeriq-backend",
-  "version": "2026.03.16",
+  "version": "2026.3.17",
   "description": "HOA LedgerIQ - Backend API",
   "private": true,
   "scripts": {
@@ -27,18 +27,26 @@
     "@nestjs/swagger": "^7.4.2",
     "@nestjs/throttler": "^6.5.0",
     "@nestjs/typeorm": "^10.0.2",
+    "@simplewebauthn/server": "^13.3.0",
     "bcryptjs": "^3.0.3",
+    "bullmq": "^5.71.0",
     "class-transformer": "^0.5.1",
     "class-validator": "^0.14.1",
+    "cookie-parser": "^1.4.7",
     "helmet": "^8.1.0",
     "ioredis": "^5.4.2",
     "newrelic": "latest",
+    "otplib": "^13.3.0",
     "passport": "^0.7.0",
+    "passport-azure-ad": "^4.3.5",
+    "passport-google-oauth20": "^2.0.0",
     "passport-jwt": "^4.0.1",
     "passport-local": "^1.0.0",
     "pg": "^8.13.1",
+    "qrcode": "^1.5.4",
     "reflect-metadata": "^0.2.2",
     "rxjs": "^7.8.1",
+    "stripe": "^20.4.1",
     "typeorm": "^0.3.20",
     "uuid": "^9.0.1"
   },
@@ -47,12 +55,15 @@
     "@nestjs/schematics": "^10.2.3",
     "@nestjs/testing": "^10.4.15",
     "@types/bcryptjs": "^2.4.6",
+    "@types/cookie-parser": "^1.4.10",
     "@types/express": "^5.0.0",
     "@types/jest": "^29.5.14",
     "@types/multer": "^2.0.0",
     "@types/node": "^20.17.12",
+    "@types/passport-google-oauth20": "^2.0.17",
     "@types/passport-jwt": "^4.0.1",
     "@types/passport-local": "^1.0.38",
+    "@types/qrcode": "^1.5.6",
     "@types/uuid": "^9.0.8",
     "jest": "^29.7.0",
     "ts-jest": "^29.2.5",