Fix TypeScript errors for Netlify Identity integration

- Add proper TypeScript types for Netlify Identity in env.d.ts
- Define NetlifyUser and NetlifyIdentity interfaces
- Fix ESLint errors by removing 'any' types
- Add optional chaining for safe access
- Apply code formatting with Prettier

All TypeScript, ESLint, and Prettier checks now pass successfully.

🤖 Generated with Claude Code

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

public/decapcms/index.html

@@ -13,10 +13,10 @@
     <script>
       // Initialize Netlify Identity widget
       if (window.netlifyIdentity) {
-        window.netlifyIdentity.on("init", user => {
+        window.netlifyIdentity.on('init', (user) => {
           if (!user) {
-            window.netlifyIdentity.on("login", () => {
-              document.location.href = "/admin/";
+            window.netlifyIdentity.on('login', () => {
+              document.location.href = '/admin/';
             });
           }
         });