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/.env.example

@@ -0,0 +1,11 @@
+# Azure OpenAI Configuration
+AZURE_OPENAI_ENDPOINT=https://your-azure-openai-endpoint.openai.azure.com
+AZURE_OPENAI_API_KEY=your-api-key-here
+AZURE_OPENAI_API_VERSION=2024-12-01-preview
+
+# Supabase Configuration
+SUPABASE_URL=https://your-project.supabase.co
+SUPABASE_SERVICE_KEY=your-service-key-here
+
+# Server Configuration
+PORT=3001