feat(chat): integrate chat project into monorepo with full app structure

- Restructure chat as apps/mobile, apps/web, apps/landing, backend
- Add NestJS backend for secure Azure OpenAI API calls
- Remove exposed API key from mobile app (security fix)
- Add shared chat-types package
- Create SvelteKit web app scaffold
- Create Astro landing page scaffold
- Update pnpm workspace configuration
- Add project-level CLAUDE.md documentation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

chat/package.json

@@ -0,0 +1,12 @@
+{
+  "name": "chat",
+  "version": "1.0.0",
+  "private": true,
+  "description": "Chat project - AI chat application with mobile, web and landing",
+  "scripts": {
+    "dev": "turbo run dev",
+    "build": "turbo run build",
+    "lint": "turbo run lint",
+    "type-check": "turbo run type-check"
+  }
+}