Add production deployment config, Alembic migration, switch to Haiku

- Production Docker Compose with Caddy reverse proxy, Gunicorn, Nginx
- Multi-stage frontend build for production
- Deploy script and automated database backup script
- Initial Alembic migration with all tables
- Switch recommendation model from Sonnet to Haiku for cost efficiency

Caddyfile

@@ -0,0 +1,19 @@
+{$DOMAIN:localhost} {
+    # Frontend
+    handle {
+        reverse_proxy frontend:80
+    }
+
+    # API
+    handle /api/* {
+        reverse_proxy backend:8000
+    }
+
+    # Security headers
+    header {
+        X-Content-Type-Options nosniff
+        X-Frame-Options DENY
+        Referrer-Policy strict-origin-when-cross-origin
+        -Server
+    }
+}