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

client/src/ui/downloads.js

@@ -75,12 +75,12 @@ export function renderDownloads() {
   }
 
   if (filteredDownloads.length === 0) {
-    noDownloads.style.display = 'block';
+    noDownloads.classList.remove('hidden');
     downloadsList.innerHTML = '';
     return;
   }
 
-  noDownloads.style.display = 'none';
+  noDownloads.classList.add('hidden');
 
   // Get existing cards
   const existingCards = new Map();