Add clone buttons, fix card navigation highlight, UI polish

- Add clone buttons to Audio Source and Value Source cards
- Fix command palette navigation destroying card highlight by skipping
  redundant data reload (skipLoad option on switchTab)
- Convert value source modal sliders to value-in-label pattern
- Change audio/value source modal footers to icon-only buttons
- Remove separator lines between card sections
- Add UI conventions to CLAUDE.md (card appearance, modal footer, sliders)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/js/features/audio-sources.js

@@ -149,6 +149,22 @@ export async function editAudioSource(sourceId) {
     }
 }
 
+// ── Clone ─────────────────────────────────────────────────────
+
+export async function cloneAudioSource(sourceId) {
+    try {
+        const resp = await fetchWithAuth(`/audio-sources/${sourceId}`);
+        if (!resp.ok) throw new Error('fetch failed');
+        const data = await resp.json();
+        delete data.id;
+        data.name = data.name + ' (copy)';
+        await showAudioSourceModal(data.source_type, data);
+    } catch (e) {
+        if (e.isAuth) return;
+        showToast(e.message, 'error');
+    }
+}
+
 // ── Delete ────────────────────────────────────────────────────
 
 export async function deleteAudioSource(sourceId) {