feat(app): add error boundaries and fix ESLint config for Vue+TS

- Wrap ChatMessage v-for loop in ChatWindow with ErrorBoundary
- Wrap ContentPanel grid/detail sections with ErrorBoundary
- Fix ESLint flat config: add vue-eslint-parser for TypeScript in SFCs
- Add browser globals to ESLint config
- Fix lint errors in contentExtraction.ts (useless escapes, prefer-const,
  unicode flag for emoji regex)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/package.json

@@ -26,18 +26,24 @@
     "vue-router": "^5.0.3"
   },
   "devDependencies": {
+    "@eslint/js": "^10.0.1",
+    "@playwright/test": "^1.49.0",
     "@tailwindcss/vite": "^4.2.1",
     "@vitejs/plugin-vue": "^6.0.4",
     "duck-duck-scrape": "^2.2.7",
     "eslint": "^10.0.2",
+    "eslint-plugin-vue": "^10.8.0",
+    "globals": "^17.4.0",
+    "happy-dom": "^20.8.3",
     "rss-parser": "^3.13.0",
     "tailwindcss": "^4.2.1",
     "tsx": "^4.21.0",
     "typescript": "~5.8.0",
+    "typescript-eslint": "^8.56.1",
     "vite": "^7.3.1",
     "vite-plugin-pwa": "^1.2.0",
-    "@playwright/test": "^1.49.0",
     "vitest": "^4.0.18",
+    "vue-eslint-parser": "^10.4.0",
     "vue-tsc": "^3.2.5"
   }
 }