Refactor monolithic modules and harden booking, email, and auth infrastructure.

Split oversized frontend API client, email service, and admin/booking pages into focused modules while preserving import surfaces, and add Redis-backed queues, stale booking cleanup, stronger auth, and scale deployment configs.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/lib/redis.ts

@@ -0,0 +1,93 @@
+// Optional Redis connection manager.
+//
+// Redis is entirely optional. When REDIS_URL is unset the app runs exactly as
+// before with in-memory backends. When set, this module owns a single shared
+// command connection plus a dedicated subscriber connection (a connection in
+// subscribe mode cannot run normal commands), with auto-reconnect, capped
+// backoff, and a health flag that callers and the health endpoint can read.
+
+import Redis from 'ioredis';
+
+let client: Redis | null = null;
+let subscriber: Redis | null = null;
+let healthy = false;
+let initialized = false;
+
+/** Whether Redis is configured via REDIS_URL. */
+export function isRedisEnabled(): boolean {
+  return !!process.env.REDIS_URL;
+}
+
+/** Whether the Redis connection is currently usable. */
+export function isRedisHealthy(): boolean {
+  return isRedisEnabled() && healthy;
+}
+
+function buildClient(label: string): Redis {
+  const url = process.env.REDIS_URL as string;
+  const instance = new Redis(url, {
+    // Keep the process responsive: fail fast on a per-command basis and let the
+    // callers degrade to their in-memory fallback rather than hanging.
+    maxRetriesPerRequest: 1,
+    enableOfflineQueue: false,
+    lazyConnect: false,
+    retryStrategy(times) {
+      // Capped exponential backoff for reconnects: 200ms, 400ms ... max 5s.
+      const delay = Math.min(times * 200, 5000);
+      return delay;
+    },
+  });
+
+  instance.on('connect', () => {
+    console.log(`[redis] (${label}) connecting`);
+  });
+  instance.on('ready', () => {
+    healthy = true;
+    console.log(`[redis] (${label}) ready`);
+  });
+  instance.on('error', (err) => {
+    healthy = false;
+    console.error(`[redis] (${label}) error:`, err?.message || err);
+  });
+  instance.on('reconnecting', () => {
+    healthy = false;
+    console.warn(`[redis] (${label}) reconnecting`);
+  });
+  instance.on('end', () => {
+    healthy = false;
+    console.warn(`[redis] (${label}) connection closed`);
+  });
+
+  return instance;
+}
+
+function ensureInit(): void {
+  if (initialized || !isRedisEnabled()) return;
+  initialized = true;
+  client = buildClient('commands');
+  subscriber = buildClient('subscriber');
+}
+
+/** Shared command connection, or null when Redis is not configured. */
+export function getRedis(): Redis | null {
+  ensureInit();
+  return client;
+}
+
+/** Dedicated subscriber connection, or null when Redis is not configured. */
+export function getSubscriber(): Redis | null {
+  ensureInit();
+  return subscriber;
+}
+
+/** Close connections (used for graceful shutdown). */
+export async function closeRedis(): Promise<void> {
+  const tasks: Promise<unknown>[] = [];
+  if (client) tasks.push(client.quit().catch(() => undefined));
+  if (subscriber) tasks.push(subscriber.quit().catch(() => undefined));
+  await Promise.all(tasks);
+  client = null;
+  subscriber = null;
+  initialized = false;
+  healthy = false;
+}