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/apps/mobile/app.json

@@ -0,0 +1,56 @@
+{
+  "expo": {
+    "name": "chat",
+    "slug": "chat",
+    "version": "1.0.0",
+    "scheme": "chat",
+    "web": {
+      "bundler": "metro",
+      "output": "server",
+      "favicon": "./assets/favicon.png"
+    },
+    "plugins": [
+      "expo-router",
+      [
+        "expo-dev-launcher",
+        {
+          "launchMode": "most-recent"
+        }
+      ]
+    ],
+    "experiments": {
+      "typedRoutes": true,
+      "tsconfigPaths": true
+    },
+    "orientation": "portrait",
+    "icon": "./assets/icon.png",
+    "userInterfaceStyle": "light",
+    "splash": {
+      "image": "./assets/splash.png",
+      "resizeMode": "contain",
+      "backgroundColor": "#ffffff"
+    },
+    "assetBundlePatterns": [
+      "**/*"
+    ],
+    "ios": {
+      "supportsTablet": true,
+      "bundleIdentifier": "com.tilljs.chat"
+    },
+    "android": {
+      "adaptiveIcon": {
+        "foregroundImage": "./assets/adaptive-icon.png",
+        "backgroundColor": "#ffffff"
+      },
+      "package": "com.tilljs.chat"
+    },
+    "extra": {
+      "router": {
+        "origin": false
+      },
+      "eas": {
+        "projectId": "67f22a8b-3cae-487d-af1f-55bdaca50e81"
+      }
+    }
+  }
+}