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>

docker-compose.yml

@@ -29,6 +29,21 @@ services:
       - NEW_RELIC_ENABLED=${NEW_RELIC_ENABLED:-false}
       - NEW_RELIC_LICENSE_KEY=${NEW_RELIC_LICENSE_KEY:-}
       - NEW_RELIC_APP_NAME=${NEW_RELIC_APP_NAME:-HOALedgerIQ_App}
+      - STRIPE_SECRET_KEY=${STRIPE_SECRET_KEY:-}
+      - STRIPE_WEBHOOK_SECRET=${STRIPE_WEBHOOK_SECRET:-}
+      - STRIPE_STARTER_PRICE_ID=${STRIPE_STARTER_PRICE_ID:-}
+      - STRIPE_PROFESSIONAL_PRICE_ID=${STRIPE_PROFESSIONAL_PRICE_ID:-}
+      - STRIPE_ENTERPRISE_PRICE_ID=${STRIPE_ENTERPRISE_PRICE_ID:-}
+      - GOOGLE_CLIENT_ID=${GOOGLE_CLIENT_ID:-}
+      - GOOGLE_CLIENT_SECRET=${GOOGLE_CLIENT_SECRET:-}
+      - GOOGLE_CALLBACK_URL=${GOOGLE_CALLBACK_URL:-http://localhost/api/auth/google/callback}
+      - AZURE_CLIENT_ID=${AZURE_CLIENT_ID:-}
+      - AZURE_CLIENT_SECRET=${AZURE_CLIENT_SECRET:-}
+      - AZURE_TENANT_ID=${AZURE_TENANT_ID:-}
+      - AZURE_CALLBACK_URL=${AZURE_CALLBACK_URL:-http://localhost/api/auth/azure/callback}
+      - WEBAUTHN_RP_ID=${WEBAUTHN_RP_ID:-localhost}
+      - WEBAUTHN_RP_ORIGIN=${WEBAUTHN_RP_ORIGIN:-http://localhost}
+      - INVITE_TOKEN_SECRET=${INVITE_TOKEN_SECRET:-dev-invite-secret}
     volumes:
       - ./backend/src:/app/src
       - ./backend/nest-cli.json:/app/nest-cli.json