Fix CSP violations and ignoreAvailable reference error

- Add .hidden utility class to style.css for CSP compliance
- Replace all inline style='display: none' with class='hidden' in HTML
- Update all UI modules to use classList.add/remove instead of style.display
- Fix ignoreAvailable reference error in history.js (use state.ignoreAvailable)
- Rebuild client bundle with vite

public/style.css

@@ -1,3 +1,8 @@
+/* ===== Utility Classes ===== */
+.hidden {
+  display: none !important;
+}
+
 /* ===== Splash Screen ===== */
 .splash-screen {
   position: fixed;