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>

eslint.config.mjs

@@ -2,9 +2,74 @@ import nextConfig from "eslint-config-next/core-web-vitals";
 
 const config = [
   {
-    ignores: [".next/**", "node_modules/**", ".cache/**", "dist/**", "build/**"],
+    ignores: [
+      ".next/**",
+      "node_modules/**",
+      ".cache/**",
+      "dist/**",
+      "build/**",
+      "create-agentic-app/**",
+      "drizzle/**",
+      "scripts/**",
+    ],
   },
   ...nextConfig,
+  {
+    rules: {
+      // React rules
+      "react/jsx-no-target-blank": "error",
+      "react/no-unescaped-entities": "off",
+
+      // React Hooks rules
+      "react-hooks/rules-of-hooks": "error",
+      "react-hooks/exhaustive-deps": "warn",
+
+      // Import rules
+      "import/no-anonymous-default-export": "warn",
+      "import/order": [
+        "warn",
+        {
+          groups: [
+            "builtin",
+            "external",
+            "internal",
+            ["parent", "sibling"],
+            "index",
+            "type",
+          ],
+          pathGroups: [
+            {
+              pattern: "react",
+              group: "builtin",
+              position: "before",
+            },
+            {
+              pattern: "next/**",
+              group: "builtin",
+              position: "before",
+            },
+            {
+              pattern: "@/**",
+              group: "internal",
+              position: "before",
+            },
+          ],
+          pathGroupsExcludedImportTypes: ["react", "next"],
+          "newlines-between": "never",
+          alphabetize: {
+            order: "asc",
+            caseInsensitive: true,
+          },
+        },
+      ],
+
+      // Best practices
+      "no-console": ["warn", { allow: ["warn", "error"] }],
+      "prefer-const": "error",
+      "no-var": "error",
+      eqeqeq: ["error", "always", { null: "ignore" }],
+    },
+  },
 ];
 
 export default config;