eat: implement Holesail-Browser enhancement plan

- Add unit tests (hostname-validator, TLDs, payload-schemas) and integration tests for message handler registry
- Refactor native host message router into handler registry (handlers/state, tunnels, ssh, rdp, backup, ca, connections)
- Add ESLint config and npm test + lint steps in CI
- Dashboard: visibility-based refresh pause, configurable refresh interval (2s/5s/10s/paused)
- Accessibility: ARIA on nav and modals, focus trap and restore, prefers-reduced-motion
- Empty states: primary action buttons for virtual hosts, servers, service tunnels
- Native host rate limiting for backup and CA operations; update SECURITY.md
- CONTRIBUTING: "Adding a new dashboard page", dev workflow; add npm run dev script

extension/dashboard/core/navigation.js

@@ -35,11 +35,19 @@ function navigateTo(page) {
 }
 
 /**
- * Attach click listeners to all `.nav-item` elements.
+ * Attach click and keyboard listeners to all `.nav-item` elements.
  * Called once during dashboard initialisation.
  */
 function setupNavigation() {
   document.querySelectorAll('.nav-item').forEach(item => {
+    item.setAttribute('role', 'button');
+    item.setAttribute('tabindex', '0');
     item.addEventListener('click', () => navigateTo(item.dataset.page));
+    item.addEventListener('keydown', (e) => {
+      if (e.key === 'Enter' || e.key === ' ') {
+        e.preventDefault();
+        navigateTo(item.dataset.page);
+      }
+    });
   });
 }