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/backend/src/app.module.ts

@@ -0,0 +1,18 @@
+import { Module } from '@nestjs/common';
+import { ConfigModule } from '@nestjs/config';
+import { ChatModule } from './chat/chat.module';
+import { ConversationModule } from './conversation/conversation.module';
+import { HealthModule } from './health/health.module';
+
+@Module({
+  imports: [
+    ConfigModule.forRoot({
+      isGlobal: true,
+      envFilePath: '.env',
+    }),
+    ChatModule,
+    ConversationModule,
+    HealthModule,
+  ],
+})
+export class AppModule {}