feat: add contacts phase 2, advanced search, vacation responder, Docker & TOTP 2FA

- Contact groups/lists, vCard import/export (RFC 6350), bulk operations
- Advanced search with JMAP filter panel, search chips, cross-mailbox queries
- Vacation responder with JMAP VacationResponse, settings tab, sidebar indicator
- TOTP two-factor authentication support
- Docker multi-stage build with standalone output and docker-compose
- CSP Report-Only headers and security headers via proxy middleware
- Virtual scrolling for large email lists
- Structured server-side logger (text/JSON, configurable level)
- 450+ tests (contacts, vCard, threads, headers, identity, components)
- Playwright E2E framework setup
- Updated README and ROADMAP with all new features

next.config.ts

@@ -1,7 +1,9 @@
 import type { NextConfig } from "next";
+import createNextIntlPlugin from "next-intl/plugin";
 
 const nextConfig: NextConfig = {
-  /* config options here */
+  output: "standalone",
 };
 
-export default nextConfig;
+const withNextIntl = createNextIntlPlugin();
+export default withNextIntl(nextConfig);