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/templates/modals/audio-source-editor.html

@@ -87,8 +87,8 @@
             </form>
         </div>
         <div class="modal-footer">
-            <button class="btn btn-secondary" onclick="closeAudioSourceModal()" data-i18n="settings.button.cancel">&times; Cancel</button>
-            <button class="btn btn-primary" onclick="saveAudioSource()" data-i18n="settings.button.save">&check; Save</button>
+            <button class="btn btn-icon btn-secondary" onclick="closeAudioSourceModal()" title="Cancel" data-i18n-title="settings.button.cancel" data-i18n-aria-label="aria.cancel">&#x2715;</button>
+            <button class="btn btn-icon btn-primary" onclick="saveAudioSource()" title="Save" data-i18n-title="settings.button.save" data-i18n-aria-label="aria.save">&#x2713;</button>
         </div>
     </div>
 </div>