feat: website widget + omnichannel lead webhooks

Widget (embeddable):
- Preact + Vite library mode → 35KB IIFE bundle served from sidecar
- Shadow DOM for CSS isolation, themed from sidecar theme API
- AI chatbot (streaming), appointment booking (4-step wizard), lead capture form
- FontAwesome Pro duotone SVGs bundled as inline strings
- HMAC-signed site keys (Redis storage, origin validation)
- Captcha guard (Cloudflare Turnstile ready)

Sidecar endpoints:
- GET/PUT/DELETE /api/widget/keys/* — site key management
- GET /api/widget/init — theme + config (key-gated)
- GET /api/widget/doctors, /slots — doctor list + availability
- POST /api/widget/book — appointment booking (captcha-gated)
- POST /api/widget/lead — lead capture (captcha-gated)

Omnichannel webhooks:
- POST /api/webhook/facebook — Meta Lead Ads (verification + lead ingestion)
- POST /api/webhook/google — Google Ads lead form extension
- POST /api/webhook/whatsapp — Ozonetel WhatsApp callback (receiver ready)
- POST /api/webhook/sms — Ozonetel SMS callback (receiver ready)

Infrastructure:
- SessionService.setCachePersistent() for non-expiring Redis keys
- Static file serving from /public (widget.js)
- WidgetModule registered in AppModule

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main.ts

@@ -1,9 +1,11 @@
 import { NestFactory } from '@nestjs/core';
+import type { NestExpressApplication } from '@nestjs/platform-express';
+import { join } from 'path';
 import { AppModule } from './app.module';
 import { ConfigService } from '@nestjs/config';
 
 async function bootstrap() {
-    const app = await NestFactory.create(AppModule);
+    const app = await NestFactory.create<NestExpressApplication>(AppModule);
     const config = app.get(ConfigService);
 
     app.enableCors({
@@ -11,6 +13,16 @@ async function bootstrap() {
         credentials: true,
     });
 
+    // Serve widget.js and other static files from /public
+    app.useStaticAssets(join(__dirname, '..', 'public'), {
+        setHeaders: (res, path) => {
+            if (path.endsWith('.js')) {
+                res.setHeader('Cache-Control', 'public, max-age=3600');
+                res.setHeader('Access-Control-Allow-Origin', '*');
+            }
+        },
+    });
+
     const port = config.get('port');
     await app.listen(port);
     console.log(`Helix Engage Server running on port ${port}`);