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/stores/pubsub.ts

@@ -0,0 +1,121 @@
+// Pub/Sub abstraction with two implementations:
+// - memory: in-process EventEmitter (single instance only)
+// - redis: PUBLISH / SUBSCRIBE so a message published on one instance reaches
+//   subscribers on every instance
+//
+// Messages are JSON-serialized. Selection happens once based on REDIS_URL.
+
+import { EventEmitter } from 'events';
+import { getRedis, getSubscriber, isRedisEnabled } from '../redis.js';
+
+export type PubSubHandler = (message: any) => void;
+
+export interface PubSub {
+  readonly backend: 'memory' | 'redis';
+  publish(channel: string, message: any): Promise<void>;
+  // Returns an unsubscribe function for this specific handler.
+  subscribe(channel: string, handler: PubSubHandler): Promise<() => void>;
+}
+
+// ==================== Memory implementation ====================
+
+class MemoryPubSub implements PubSub {
+  readonly backend = 'memory' as const;
+  private emitter = new EventEmitter();
+
+  constructor() {
+    // SSE fan-out can attach many listeners to the same channel; lift the cap.
+    this.emitter.setMaxListeners(0);
+  }
+
+  async publish(channel: string, message: any): Promise<void> {
+    this.emitter.emit(channel, message);
+  }
+
+  async subscribe(channel: string, handler: PubSubHandler): Promise<() => void> {
+    this.emitter.on(channel, handler);
+    return () => this.emitter.off(channel, handler);
+  }
+}
+
+// ==================== Redis implementation ====================
+
+class RedisPubSub implements PubSub {
+  readonly backend = 'redis' as const;
+  // Per-channel handler sets so a single Redis subscription fans out locally.
+  private handlers = new Map<string, Set<PubSubHandler>>();
+  private wired = false;
+
+  private ensureWired(): void {
+    if (this.wired) return;
+    const sub = getSubscriber();
+    if (!sub) return;
+    this.wired = true;
+    sub.on('message', (channel: string, payload: string) => {
+      const set = this.handlers.get(channel);
+      if (!set || set.size === 0) return;
+      let parsed: any = payload;
+      try {
+        parsed = JSON.parse(payload);
+      } catch {
+        // Leave as raw string if it was not JSON.
+      }
+      for (const handler of set) {
+        try {
+          handler(parsed);
+        } catch (err: any) {
+          console.error('[pubsub] handler error:', err?.message || err);
+        }
+      }
+    });
+  }
+
+  async publish(channel: string, message: any): Promise<void> {
+    const redis = getRedis();
+    if (!redis) return;
+    try {
+      await redis.publish(channel, JSON.stringify(message));
+    } catch (err: any) {
+      console.error('[pubsub] publish error:', err?.message || err);
+    }
+  }
+
+  async subscribe(channel: string, handler: PubSubHandler): Promise<() => void> {
+    this.ensureWired();
+    const sub = getSubscriber();
+    if (!sub) return () => undefined;
+
+    let set = this.handlers.get(channel);
+    if (!set) {
+      set = new Set();
+      this.handlers.set(channel, set);
+      try {
+        await sub.subscribe(channel);
+      } catch (err: any) {
+        console.error('[pubsub] subscribe error:', err?.message || err);
+      }
+    }
+    set.add(handler);
+
+    return () => {
+      const current = this.handlers.get(channel);
+      if (!current) return;
+      current.delete(handler);
+      if (current.size === 0) {
+        this.handlers.delete(channel);
+        sub.unsubscribe(channel).catch(() => undefined);
+      }
+    };
+  }
+}
+
+// ==================== Selection ====================
+
+let instance: PubSub | null = null;
+
+export function getPubSub(): PubSub {
+  if (!instance) {
+    instance = isRedisEnabled() ? new RedisPubSub() : new MemoryPubSub();
+  }
+  return instance;
+}