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/css/streams.css

@@ -627,7 +627,6 @@
     color: var(--text-secondary);
     margin: 0 0 12px 0;
     padding-bottom: 8px;
-    border-bottom: 1px solid var(--border-color);
 }
 
 .subtab-section-header.cs-header {