feat: comprehensive boilerplate improvements

Security & Stability:
- Add Next.js 16 proxy.ts for BetterAuth cookie-based auth protection
- Add rate limiting for API routes (src/lib/rate-limit.ts)
- Add Zod validation for chat API request bodies
- Add session auth check to chat and diagnostics endpoints
- Add security headers in next.config.ts (CSP, X-Frame-Options, etc.)
- Add file upload validation and sanitization in storage.ts

Core UX Components:
- Add error boundaries (error.tsx, not-found.tsx, chat/error.tsx)
- Add loading states (skeleton.tsx, spinner.tsx, loading.tsx files)
- Add toast notifications with Sonner
- Add form components (input.tsx, textarea.tsx, label.tsx)
- Add database indexes for performance (schema.ts)
- Enhance chat UX: timestamps, copy-to-clipboard, thinking indicator,
  error display, localStorage message persistence

Polish & Accessibility:
- Add Open Graph and Twitter card metadata
- Add JSON-LD structured data for SEO
- Add sitemap.ts, robots.ts, manifest.ts
- Add skip-to-content link and ARIA labels in site-header
- Enable profile page quick action buttons with dialogs
- Update Next.js 15 references to Next.js 16

Developer Experience:
- Add GitHub Actions CI workflow (lint, typecheck, build)
- Add Prettier configuration (.prettierrc, .prettierignore)
- Add .nvmrc pinning Node 20
- Add ESLint rules: import/order, react-hooks/exhaustive-deps
- Add stricter TypeScript settings (exactOptionalPropertyTypes,
  noImplicitOverride)
- Add interactive setup script (scripts/setup.ts)
- Add session utility functions (src/lib/session.ts)

All changes mirrored to create-agentic-app/template/

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

create-agentic-app/template/package.json

@@ -2,11 +2,16 @@
   "name": "agentic-coding-starter-kit",
   "version": "1.1.2",
   "scripts": {
-    "dev": "next dev",
+    "dev": "next dev --turbopack",
     "build": "pnpm run db:migrate && next build",
     "start": "next start",
     "lint": "eslint .",
     "typecheck": "tsc --noEmit",
+    "check": "pnpm lint && pnpm typecheck",
+    "format": "prettier --write .",
+    "format:check": "prettier --check .",
+    "setup": "npx tsx scripts/setup.ts",
+    "env:check": "node -e \"require('./src/lib/env.ts').checkEnv()\" || echo 'Run with tsx: npx tsx -e \"import { checkEnv } from './src/lib/env'; checkEnv();\"'",
     "db:generate": "drizzle-kit generate",
     "db:migrate": "drizzle-kit migrate",
     "db:push": "drizzle-kit push",
@@ -15,12 +20,12 @@
     "db:reset": "drizzle-kit drop && drizzle-kit push"
   },
   "dependencies": {
-    "@ai-sdk/openai": "^2.0.60",
     "@ai-sdk/react": "^2.0.86",
     "@openrouter/ai-sdk-provider": "^1.2.0",
     "@radix-ui/react-avatar": "^1.1.10",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-dropdown-menu": "^2.1.16",
+    "@radix-ui/react-label": "^2.1.8",
     "@radix-ui/react-slot": "^1.2.3",
     "@vercel/blob": "^2.0.0",
     "ai": "^5.0.86",
@@ -36,6 +41,7 @@
     "react": "19.2.0",
     "react-dom": "19.2.0",
     "react-markdown": "^10.1.0",
+    "sonner": "^2.0.7",
     "tailwind-merge": "^3.3.1",
     "zod": "^4.1.12"
   },
@@ -48,8 +54,11 @@
     "drizzle-kit": "^0.31.6",
     "eslint": "^9.39.0",
     "eslint-config-next": "16.0.3",
+    "prettier": "^3.4.2",
+    "prettier-plugin-tailwindcss": "^0.6.9",
     "shadcn": "^3.5.0",
     "tailwindcss": "^4.1.16",
+    "tsx": "^4.19.2",
     "tw-animate-css": "^1.4.0",
     "typescript": "^5.9.3"
   },