Comprehensive WebUI review: 41 UX/feature/CSS improvements

Safety & Correctness:
- Add confirmation dialogs to Stop All, turnOffDevice
- i18n confirm dialog (title, yes, no buttons)
- Fix duplicate tutorial-overlay ID
- Define missing CSS variables (--radius, --text-primary, --hover-bg, --input-bg)
- Fix toast z-index conflict with confirm dialog (2500 → 3000)

UX Consistency:
- Add backdrop-close to test modals
- Add device clone feature (only entity without it)
- Add sync clocks to command palette
- Replace 20+ hardcoded accent colors with CSS vars/color-mix()
- Remove dead .badge duplicate from components.css
- Make calibration elements keyboard-accessible (div → button)
- Add aria-labels to color picker swatches
- Fix pattern canvas mobile horizontal scroll
- Fix graph editor mobile bottom clipping

Polish:
- Add empty-state messages to all CardSection instances
- Convert 21 px font-sizes to rem
- Add scroll-behavior: smooth with reduced-motion override
- Add @media print styles
- Add :focus-visible to 4 missing interactive elements
- Fix settings modal close label (Cancel → Close)
- Fix api-key submit button i18n

New Features:
- Command palette actions: start/stop targets, activate scenes, enable/disable
- Bulk start/stop API endpoints (POST /output-targets/bulk/start|stop)
- OS notification history viewer modal
- Scene "used by" automation reference count on cards
- Clock elapsed time display on Streams tab cards
- Device "last seen" relative timestamp on cards
- Audio device refresh button in edit modal
- Composite layer drag-to-reorder
- MQTT settings panel (broker config with JSON persistence)
- WebSocket log viewer with level filtering and ring buffer
- Runtime log-level adjustment (GET/PUT endpoints + settings UI)
- Animated value source waveform canvas preview
- Gradient custom preset save/delete (localStorage)
- API key read-only display in settings
- Backup metadata (file size, auto/manual badges)
- Server restart button with confirm + overlay
- Partial config export/import per entity type
- Progressive disclosure in target editor (Advanced section)

CSS Architecture:
- Define radius scale tokens (--radius-sm/md/lg/pill)
- Scope .cs-filter selectors to remove 7 !important overrides
- Consolidate duplicate toggle switch (filter-list → settings-toggle)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/src/wled_controller/static/js/features/targets.js

@@ -40,10 +40,10 @@ import { updateSubTabHash, updateTabBadge } from './tabs.js';
 // (pattern-templates.js calls window.loadTargetsTab)
 
 // ── Card section instances ──
-const csDevices = new CardSection('led-devices', { titleKey: 'targets.section.devices', gridClass: 'devices-grid', addCardOnclick: "showAddDevice()", keyAttr: 'data-device-id' });
-const csLedTargets = new CardSection('led-targets', { titleKey: 'targets.section.targets', gridClass: 'devices-grid', addCardOnclick: "showTargetEditor()", keyAttr: 'data-target-id', headerExtra: `<button class="btn btn-sm btn-danger" onclick="event.stopPropagation(); stopAllLedTargets()" data-stop-all="led" data-i18n-title="targets.stop_all.button" data-i18n-aria-label="targets.stop_all.button">${ICON_STOP}</button>` });
-const csKCTargets = new CardSection('kc-targets', { titleKey: 'targets.section.key_colors', gridClass: 'devices-grid', addCardOnclick: "showKCEditor()", keyAttr: 'data-kc-target-id', headerExtra: `<button class="btn btn-sm btn-danger" onclick="event.stopPropagation(); stopAllKCTargets()" data-stop-all="kc" data-i18n-title="targets.stop_all.button" data-i18n-aria-label="targets.stop_all.button">${ICON_STOP}</button>` });
-const csPatternTemplates = new CardSection('kc-patterns', { titleKey: 'targets.section.pattern_templates', gridClass: 'templates-grid', addCardOnclick: "showPatternTemplateEditor()", keyAttr: 'data-pattern-template-id' });
+const csDevices = new CardSection('led-devices', { titleKey: 'targets.section.devices', gridClass: 'devices-grid', addCardOnclick: "showAddDevice()", keyAttr: 'data-device-id', emptyKey: 'section.empty.devices' });
+const csLedTargets = new CardSection('led-targets', { titleKey: 'targets.section.targets', gridClass: 'devices-grid', addCardOnclick: "showTargetEditor()", keyAttr: 'data-target-id', emptyKey: 'section.empty.targets', headerExtra: `<button class="btn btn-sm btn-danger" onclick="event.stopPropagation(); stopAllLedTargets()" data-stop-all="led" data-i18n-title="targets.stop_all.button" data-i18n-aria-label="targets.stop_all.button">${ICON_STOP}</button>` });
+const csKCTargets = new CardSection('kc-targets', { titleKey: 'targets.section.key_colors', gridClass: 'devices-grid', addCardOnclick: "showKCEditor()", keyAttr: 'data-kc-target-id', emptyKey: 'section.empty.kc_targets', headerExtra: `<button class="btn btn-sm btn-danger" onclick="event.stopPropagation(); stopAllKCTargets()" data-stop-all="kc" data-i18n-title="targets.stop_all.button" data-i18n-aria-label="targets.stop_all.button">${ICON_STOP}</button>` });
+const csPatternTemplates = new CardSection('kc-patterns', { titleKey: 'targets.section.pattern_templates', gridClass: 'templates-grid', addCardOnclick: "showPatternTemplateEditor()", keyAttr: 'data-pattern-template-id', emptyKey: 'section.empty.pattern_templates' });
 
 // Re-render targets tab when language changes (only if tab is active)
 document.addEventListener('languageChanged', () => {
@@ -189,8 +189,12 @@ function _updateSpecificSettingsVisibility() {
     const deviceSelect = document.getElementById('target-editor-device');
     const selectedDevice = _targetEditorDevices.find(d => d.id === deviceSelect.value);
     const isWled = !selectedDevice || selectedDevice.device_type === 'wled';
-    // Hide entire Specific Settings section for non-WLED devices (protocol + keepalive are WLED-only)
-    document.getElementById('target-editor-device-settings').style.display = isWled ? '' : 'none';
+    // Hide WLED-only controls (protocol + keepalive) for non-WLED devices
+    const protocolGroup = document.getElementById('target-editor-protocol-group');
+    if (protocolGroup) protocolGroup.style.display = isWled ? '' : 'none';
+    // keepalive is controlled further by _updateKeepaliveVisibility
+    const keepaliveGroup = document.getElementById('target-editor-keepalive-group');
+    if (keepaliveGroup && !isWled) keepaliveGroup.style.display = 'none';
 }
 
 function _updateBrightnessThresholdVisibility() {
@@ -1069,10 +1073,14 @@ export async function stopTargetProcessing(targetId) {
 }
 
 export async function stopAllLedTargets() {
+    const confirmed = await showConfirm(t('confirm.stop_all'));
+    if (!confirmed) return;
     await _stopAllByType('led');
 }
 
 export async function stopAllKCTargets() {
+    const confirmed = await showConfirm(t('confirm.stop_all'));
+    if (!confirmed) return;
     await _stopAllByType('key_colors');
 }