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/package.json

@@ -0,0 +1,43 @@
+{
+  "name": "@chat/backend",
+  "version": "1.0.0",
+  "private": true,
+  "scripts": {
+    "build": "nest build",
+    "start": "nest start",
+    "start:dev": "nest start --watch",
+    "start:debug": "nest start --debug --watch",
+    "start:prod": "node dist/main",
+    "lint": "eslint \"{src,apps,libs,test}/**/*.ts\" --fix",
+    "type-check": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@nestjs/common": "^10.4.15",
+    "@nestjs/config": "^3.3.0",
+    "@nestjs/core": "^10.4.15",
+    "@nestjs/platform-express": "^10.4.15",
+    "@supabase/supabase-js": "^2.47.10",
+    "class-transformer": "^0.5.1",
+    "class-validator": "^0.14.1",
+    "openai": "^4.77.0",
+    "reflect-metadata": "^0.2.2",
+    "rxjs": "^7.8.1"
+  },
+  "devDependencies": {
+    "@nestjs/cli": "^10.4.9",
+    "@nestjs/schematics": "^10.2.3",
+    "@types/express": "^5.0.0",
+    "@types/node": "^22.10.2",
+    "@typescript-eslint/eslint-plugin": "^8.18.1",
+    "@typescript-eslint/parser": "^8.18.1",
+    "eslint": "^9.17.0",
+    "eslint-config-prettier": "^9.1.0",
+    "eslint-plugin-prettier": "^5.2.1",
+    "prettier": "^3.4.2",
+    "source-map-support": "^0.5.21",
+    "ts-loader": "^9.5.1",
+    "ts-node": "^10.9.2",
+    "tsconfig-paths": "^4.2.0",
+    "typescript": "^5.7.2"
+  }
+}