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/streams.js

@@ -41,7 +41,7 @@ import {
 import { API_BASE, getHeaders, fetchWithAuth, escapeHtml } from '../core/api.js';
 import { t } from '../core/i18n.js';
 import { Modal } from '../core/modal.js';
-import { showToast, showConfirm, openLightbox, openFullImageLightbox, showOverlaySpinner, hideOverlaySpinner, updateOverlayPreview, setTabRefreshing } from '../core/ui.js';
+import { showToast, showConfirm, openLightbox, openFullImageLightbox, showOverlaySpinner, hideOverlaySpinner, updateOverlayPreview, setTabRefreshing, setupBackdropClose } from '../core/ui.js';
 import { openDisplayPicker, formatDisplayLabel } from './displays.js';
 import { CardSection } from '../core/card-sections.js';
 import { TreeNav } from '../core/tree-nav.js';
@@ -70,19 +70,19 @@ let _audioTemplateTagsInput = null;
 let _csptTagsInput = null;
 
 // ── Card section instances ──
-const csRawStreams = new CardSection('raw-streams', { titleKey: 'streams.section.streams', gridClass: 'templates-grid', addCardOnclick: "showAddStreamModal('raw')", keyAttr: 'data-stream-id' });
-const csRawTemplates = new CardSection('raw-templates', { titleKey: 'templates.title', gridClass: 'templates-grid', addCardOnclick: "showAddTemplateModal()", keyAttr: 'data-template-id' });
-const csProcStreams = new CardSection('proc-streams', { titleKey: 'streams.section.streams', gridClass: 'templates-grid', addCardOnclick: "showAddStreamModal('processed')", keyAttr: 'data-stream-id' });
-const csProcTemplates = new CardSection('proc-templates', { titleKey: 'postprocessing.title', gridClass: 'templates-grid', addCardOnclick: "showAddPPTemplateModal()", keyAttr: 'data-pp-template-id' });
-const csAudioMulti = new CardSection('audio-multi', { titleKey: 'audio_source.group.multichannel', gridClass: 'templates-grid', addCardOnclick: "showAudioSourceModal('multichannel')", keyAttr: 'data-id' });
-const csAudioMono = new CardSection('audio-mono', { titleKey: 'audio_source.group.mono', gridClass: 'templates-grid', addCardOnclick: "showAudioSourceModal('mono')", keyAttr: 'data-id' });
-const csStaticStreams = new CardSection('static-streams', { titleKey: 'streams.group.static_image', gridClass: 'templates-grid', addCardOnclick: "showAddStreamModal('static_image')", keyAttr: 'data-stream-id' });
-const csVideoStreams = new CardSection('video-streams', { titleKey: 'streams.group.video', gridClass: 'templates-grid', addCardOnclick: "showAddStreamModal('video')", keyAttr: 'data-stream-id' });
-const csAudioTemplates = new CardSection('audio-templates', { titleKey: 'audio_template.title', gridClass: 'templates-grid', addCardOnclick: "showAddAudioTemplateModal()", keyAttr: 'data-audio-template-id' });
-const csColorStrips = new CardSection('color-strips', { titleKey: 'targets.section.color_strips', gridClass: 'templates-grid', addCardOnclick: "showCSSEditor()", keyAttr: 'data-css-id' });
-const csValueSources = new CardSection('value-sources', { titleKey: 'value_source.group.title', gridClass: 'templates-grid', addCardOnclick: "showValueSourceModal()", keyAttr: 'data-id' });
-const csSyncClocks = new CardSection('sync-clocks', { titleKey: 'sync_clock.group.title', gridClass: 'templates-grid', addCardOnclick: "showSyncClockModal()", keyAttr: 'data-id' });
-const csCSPTemplates = new CardSection('css-proc-templates', { titleKey: 'css_processing.title', gridClass: 'templates-grid', addCardOnclick: "showAddCSPTModal()", keyAttr: 'data-cspt-id' });
+const csRawStreams = new CardSection('raw-streams', { titleKey: 'streams.section.streams', gridClass: 'templates-grid', addCardOnclick: "showAddStreamModal('raw')", keyAttr: 'data-stream-id', emptyKey: 'section.empty.picture_sources' });
+const csRawTemplates = new CardSection('raw-templates', { titleKey: 'templates.title', gridClass: 'templates-grid', addCardOnclick: "showAddTemplateModal()", keyAttr: 'data-template-id', emptyKey: 'section.empty.capture_templates' });
+const csProcStreams = new CardSection('proc-streams', { titleKey: 'streams.section.streams', gridClass: 'templates-grid', addCardOnclick: "showAddStreamModal('processed')", keyAttr: 'data-stream-id', emptyKey: 'section.empty.picture_sources' });
+const csProcTemplates = new CardSection('proc-templates', { titleKey: 'postprocessing.title', gridClass: 'templates-grid', addCardOnclick: "showAddPPTemplateModal()", keyAttr: 'data-pp-template-id', emptyKey: 'section.empty.pp_templates' });
+const csAudioMulti = new CardSection('audio-multi', { titleKey: 'audio_source.group.multichannel', gridClass: 'templates-grid', addCardOnclick: "showAudioSourceModal('multichannel')", keyAttr: 'data-id', emptyKey: 'section.empty.audio_sources' });
+const csAudioMono = new CardSection('audio-mono', { titleKey: 'audio_source.group.mono', gridClass: 'templates-grid', addCardOnclick: "showAudioSourceModal('mono')", keyAttr: 'data-id', emptyKey: 'section.empty.audio_sources' });
+const csStaticStreams = new CardSection('static-streams', { titleKey: 'streams.group.static_image', gridClass: 'templates-grid', addCardOnclick: "showAddStreamModal('static_image')", keyAttr: 'data-stream-id', emptyKey: 'section.empty.picture_sources' });
+const csVideoStreams = new CardSection('video-streams', { titleKey: 'streams.group.video', gridClass: 'templates-grid', addCardOnclick: "showAddStreamModal('video')", keyAttr: 'data-stream-id', emptyKey: 'section.empty.picture_sources' });
+const csAudioTemplates = new CardSection('audio-templates', { titleKey: 'audio_template.title', gridClass: 'templates-grid', addCardOnclick: "showAddAudioTemplateModal()", keyAttr: 'data-audio-template-id', emptyKey: 'section.empty.audio_templates' });
+const csColorStrips = new CardSection('color-strips', { titleKey: 'targets.section.color_strips', gridClass: 'templates-grid', addCardOnclick: "showCSSEditor()", keyAttr: 'data-css-id', emptyKey: 'section.empty.color_strips' });
+const csValueSources = new CardSection('value-sources', { titleKey: 'value_source.group.title', gridClass: 'templates-grid', addCardOnclick: "showValueSourceModal()", keyAttr: 'data-id', emptyKey: 'section.empty.value_sources' });
+const csSyncClocks = new CardSection('sync-clocks', { titleKey: 'sync_clock.group.title', gridClass: 'templates-grid', addCardOnclick: "showSyncClockModal()", keyAttr: 'data-id', emptyKey: 'section.empty.sync_clocks' });
+const csCSPTemplates = new CardSection('css-proc-templates', { titleKey: 'css_processing.title', gridClass: 'templates-grid', addCardOnclick: "showAddCSPTModal()", keyAttr: 'data-cspt-id', emptyKey: 'section.empty.cspt' });
 
 // Re-render picture sources when language changes
 document.addEventListener('languageChanged', () => { if (apiKey) loadPictureSources(); });
@@ -322,6 +322,7 @@ export async function showTestTemplateModal(templateId) {
         restoreCaptureDuration();
 
         testTemplateModal.open();
+        setupBackdropClose(testTemplateModal.el, () => closeTestTemplateModal());
     } catch (error) {
         if (error.isAuth) return;
         showToast(t('templates.error.load'), 'error');
@@ -2162,6 +2163,7 @@ export async function showTestStreamModal(streamId) {
     restoreStreamTestDuration();
 
     testStreamModal.open();
+    setupBackdropClose(testStreamModal.el, () => closeTestStreamModal());
 }
 
 export function closeTestStreamModal() {
@@ -2229,6 +2231,7 @@ export async function showTestPPTemplateModal(templateId) {
     });
 
     testPPTemplateModal.open();
+    setupBackdropClose(testPPTemplateModal.el, () => closeTestPPTemplateModal());
 }
 
 export function closeTestPPTemplateModal() {