Feat: Update visitor tracking API and add age verification to apps

- Update visitor-tracking.js to use new API at users.unityailab.com
- Add localhost proxy detection for dev environment CORS handling
- Add age verification system to /apps page
- Add total unique visitors counter to main index page
- Fix 0-count display bug (JavaScript falsy value issue)
- Add Vite dev server proxy and URL rewriting for multi-page app

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

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

Author: hackall360

ai/index.html

@@ -555,7 +555,7 @@ <h6 class="footer-title">Connect</h6>
             async function updateVisitorCount() {
                 try {
                     const count = await VisitorTracking.getVisitorCount('demo');
-                    if (count) {
+                    if (count !== null) {
                         // Only update if count has changed or is first load
                         if (currentCount !== count) {
                             countElement.textContent = count;