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/widget/widget.types.ts

@@ -0,0 +1,38 @@
+export type WidgetSiteKey = {
+    siteId: string;
+    hospitalName: string;
+    allowedOrigins: string[];
+    active: boolean;
+    createdAt: string;
+};
+
+export type WidgetInitResponse = {
+    brand: { name: string; logo: string };
+    colors: { primary: string; primaryLight: string; text: string; textLight: string };
+    captchaSiteKey: string;
+};
+
+export type WidgetBookRequest = {
+    departmentId: string;
+    doctorId: string;
+    scheduledAt: string;
+    patientName: string;
+    patientPhone: string;
+    age?: string;
+    gender?: string;
+    chiefComplaint?: string;
+    captchaToken: string;
+};
+
+export type WidgetLeadRequest = {
+    name: string;
+    phone: string;
+    interest?: string;
+    message?: string;
+    captchaToken: string;
+};
+
+export type WidgetChatRequest = {
+    messages: Array<{ role: string; content: string }>;
+    captchaToken?: string;
+};