Add empty-state designs for empty playlists and history

Replaces bare status text with visual empty-state components:
- History: clock icon, 'Nothing watched yet' title, description, 'Search videos' CTA
- Playlist: music icon, 'This playlist is empty' title, description with tip, 'Browse videos' CTA
- Search: unchanged (hero landing handles this case)
- CTA buttons navigate to search view for quick action

frontend/app.js

@@ -596,11 +596,44 @@ function renderList() {
   }
 
   if (!list.length) {
-    els.status.classList.remove('hidden');
-    els.status.textContent =
-      view.type === 'search' ? 'Search for something to begin.'
-      : view.type === 'history' ? 'Nothing watched yet.'
-      : 'This playlist is empty. Add videos from search.';
+    els.status.classList.add('hidden');
+    els.cards.innerHTML = '';
+    const empty = document.createElement('div');
+    empty.className = 'empty-state';
+
+    if (view.type === 'search') {
+      // Hero landing is already in the player pane — list pane stays bare.
+      els.status.classList.remove('hidden');
+      els.status.textContent = 'Search for something to begin.';
+      return;
+    }
+
+    if (view.type === 'history') {
+      empty.innerHTML = `
+        <div class="empty-icon">🕘</div>
+        <h3 class="empty-title">Nothing watched yet</h3>
+        <p class="empty-desc">Your viewing history shows up here once you start playing videos.</p>
+      `;
+      const cta = document.createElement('button');
+      cta.className = 'empty-cta';
+      cta.textContent = '🔍  Search videos';
+      cta.addEventListener('click', () => { view = { type: 'search' }; render(); });
+      empty.appendChild(cta);
+    } else {
+      // Playlist view — empty
+      empty.innerHTML = `
+        <div class="empty-icon">🎵</div>
+        <h3 class="empty-title">This playlist is empty</h3>
+        <p class="empty-desc">Add videos from search results or use the <strong>+ Playlist</strong> button while playing.</p>
+      `;
+      const cta = document.createElement('button');
+      cta.className = 'empty-cta';
+      cta.textContent = '🔍  Browse videos';
+      cta.addEventListener('click', () => { view = { type: 'search' }; render(); });
+      empty.appendChild(cta);
+    }
+
+    els.cards.appendChild(empty);
     return;
   }
   els.status.classList.add('hidden');