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/locales/zh.json

@@ -29,6 +29,7 @@
   "auth.toggle_password": "切换密码可见性",
   "auth.prompt_enter": "Enter your API key:",
   "auth.prompt_update": "Current API key is set. Enter new key to update or leave blank to remove:",
+  "api_key.login": "登录",
   "displays.title": "可用显示器",
   "displays.layout": "显示器",
   "displays.information": "显示器信息",
@@ -291,6 +292,12 @@
   "device.health.offline": "离线",
   "device.health.streaming_unreachable": "流传输期间不可达",
   "device.health.checking": "检测中...",
+  "device.last_seen.label": "最近检测",
+  "device.last_seen.just_now": "刚刚",
+  "device.last_seen.seconds": "%d秒前",
+  "device.last_seen.minutes": "%d分钟前",
+  "device.last_seen.hours": "%d小时前",
+  "device.last_seen.days": "%d天前",
   "device.tutorial.start": "开始教程",
   "device.tip.metadata": "设备信息（LED 数量、类型、颜色通道）从设备自动检测",
   "device.tip.brightness": "滑动调节设备亮度",
@@ -405,6 +412,8 @@
   "confirm.title": "确认操作",
   "confirm.yes": "是",
   "confirm.no": "否",
+  "confirm.stop_all": "停止所有运行中的目标？",
+  "confirm.turn_off_device": "关闭此设备？",
   "common.loading": "加载中...",
   "common.delete": "删除",
   "common.edit": "编辑",
@@ -584,6 +593,7 @@
   "targets.section.color_strips": "色带源",
   "targets.section.targets": "目标",
   "targets.section.specific_settings": "特定设置",
+  "targets.section.advanced": "高级",
   "targets.add": "添加目标",
   "targets.edit": "编辑目标",
   "targets.loading": "正在加载目标...",
@@ -953,6 +963,11 @@
   "color_strip.gradient.preset.cool": "冷色",
   "color_strip.gradient.preset.neon": "霓虹",
   "color_strip.gradient.preset.pastel": "柔和",
+  "color_strip.gradient.preset.save_button": "保存为预设…",
+  "color_strip.gradient.preset.save_prompt": "输入预设名称：",
+  "color_strip.gradient.preset.saved": "预设已保存",
+  "color_strip.gradient.preset.deleted": "预设已删除",
+  "color_strip.gradient.preset.apply": "应用",
   "color_strip.animation": "动画",
   "color_strip.animation.type": "效果：",
   "color_strip.animation.type.hint": "要应用的动画效果。",
@@ -1043,6 +1058,15 @@
   "color_strip.notification.test.ok": "通知已发送",
   "color_strip.notification.test.no_streams": "此源没有运行中的流",
   "color_strip.notification.test.error": "发送通知失败",
+  "color_strip.notification.history.title": "通知历史",
+  "color_strip.notification.history.hint": "监听器捕获的最近OS通知（最新在前），最多50条。",
+  "color_strip.notification.history.empty": "尚未捕获任何通知",
+  "color_strip.notification.history.unavailable": "此平台不支持OS通知监听器",
+  "color_strip.notification.history.error": "加载通知历史失败",
+  "color_strip.notification.history.refresh": "刷新",
+  "color_strip.notification.history.unknown_app": "未知应用",
+  "color_strip.notification.history.fired": "触发的流数量",
+  "color_strip.notification.history.filtered": "过滤的流数量",
   "color_strip.test.title": "预览测试",
   "color_strip.test.connecting": "连接中...",
   "color_strip.test.error": "无法连接到预览流",
@@ -1188,6 +1212,7 @@
   "audio_source.type.mono": "单声道",
   "audio_source.device": "音频设备：",
   "audio_source.device.hint": "音频输入源。回环设备采集系统音频输出；输入设备采集麦克风或线路输入。",
+  "audio_source.refresh_devices": "刷新设备",
   "audio_source.parent": "父源：",
   "audio_source.parent.hint": "要从中提取通道的多声道源",
   "audio_source.channel": "通道：",
@@ -1375,6 +1400,13 @@
   "search.group.value": "值源",
   "search.group.scenes": "场景预设",
   "search.group.cspt": "色带处理模板",
+  "search.group.sync_clocks": "同步时钟",
+  "search.group.actions": "操作",
+  "search.action.start": "启动",
+  "search.action.stop": "停止",
+  "search.action.activate": "激活",
+  "search.action.enable": "启用",
+  "search.action.disable": "禁用",
   "settings.backup.label": "备份配置",
   "settings.backup.hint": "将所有配置（设备、目标、流、模板、自动化）下载为单个 JSON 文件。",
   "settings.backup.button": "下载备份",
@@ -1388,7 +1420,15 @@
   "settings.restore.error": "恢复失败",
   "settings.restore.restarting": "服务器正在重启...",
   "settings.restore.restart_timeout": "服务器未响应。请手动刷新页面。",
+  "settings.restart_server": "重启服务器",
+  "settings.restart_confirm": "重启服务器？活跃的目标将被停止。",
+  "settings.restarting": "正在重启服务器...",
   "settings.button.close": "关闭",
+  "settings.log_level.label": "日志级别",
+  "settings.log_level.hint": "实时更改服务器日志详细程度。DEBUG 显示最多细节；CRITICAL 仅显示致命错误。",
+  "settings.log_level.save": "应用",
+  "settings.log_level.saved": "日志级别已更改",
+  "settings.log_level.save_error": "更改日志级别失败",
   "settings.auto_backup.label": "自动备份",
   "settings.auto_backup.hint": "自动定期创建所有配置的备份。当达到最大数量时，旧备份会被自动清理。",
   "settings.auto_backup.enable": "启用自动备份",
@@ -1407,6 +1447,32 @@
   "settings.saved_backups.delete": "删除",
   "settings.saved_backups.delete_confirm": "删除此备份文件？",
   "settings.saved_backups.delete_error": "删除备份失败",
+  "settings.saved_backups.type.auto": "自动",
+  "settings.saved_backups.type.manual": "手动",
+  "settings.mqtt.label": "MQTT",
+  "settings.mqtt.hint": "配置 MQTT 代理连接，用于自动化条件和触发器。",
+  "settings.mqtt.enabled": "启用 MQTT",
+  "settings.mqtt.host_label": "代理主机",
+  "settings.mqtt.port_label": "端口",
+  "settings.mqtt.username_label": "用户名",
+  "settings.mqtt.password_label": "密码",
+  "settings.mqtt.password_set_hint": "已设置密码 — 留空以保留",
+  "settings.mqtt.client_id_label": "客户端 ID",
+  "settings.mqtt.base_topic_label": "基础主题",
+  "settings.mqtt.save": "保存 MQTT 设置",
+  "settings.mqtt.saved": "MQTT 设置已保存",
+  "settings.mqtt.save_error": "保存 MQTT 设置失败",
+  "settings.mqtt.error_host_required": "代理主机不能为空",
+  "settings.logs.label": "服务器日志",
+  "settings.logs.hint": "实时查看服务器日志。使用过滤器显示所需的日志级别。",
+  "settings.logs.connect": "连接",
+  "settings.logs.disconnect": "断开",
+  "settings.logs.clear": "清除",
+  "settings.logs.error": "日志查看器连接失败",
+  "settings.logs.filter.all": "所有级别",
+  "settings.logs.filter.info": "Info+",
+  "settings.logs.filter.warning": "Warning+",
+  "settings.logs.filter.error": "仅错误",
   "device.error.power_off_failed": "关闭设备失败",
   "device.removed": "设备已移除",
   "device.error.remove_failed": "移除设备失败",
@@ -1415,6 +1481,7 @@
   "device.error.required": "请填写所有字段",
   "device.error.update": "更新设备失败",
   "device.error.save": "保存设置失败",
+  "device.error.clone_failed": "克隆设备失败",
   "device_discovery.error.fill_all_fields": "请填写所有字段",
   "device_discovery.added": "设备添加成功",
   "device_discovery.error.add_failed": "添加设备失败",
@@ -1506,6 +1573,7 @@
   "sync_clock.resumed": "时钟已恢复",
   "sync_clock.reset_done": "时钟已重置为零",
   "sync_clock.delete.confirm": "删除此同步时钟？关联的源将失去同步并以默认速度运行。",
+  "sync_clock.elapsed": "已用时间",
   "color_strip.clock": "同步时钟：",
   "color_strip.clock.hint": "关联同步时钟以在多个源之间同步动画。速度在时钟上控制。",
   "graph.title": "图表",
@@ -1570,5 +1638,50 @@
   "graph.help.right_click_desc": "断开连接",
   "automation.enabled": "自动化已启用",
   "automation.disabled": "自动化已禁用",
-  "scene_preset.activated": "预设已激活"
+  "scene_preset.activated": "预设已激活",
+  "scene_preset.used_by": "被 %d 个自动化使用",
+  "settings.api_keys.label": "API 密钥",
+  "settings.api_keys.hint": "API 密钥在服务器配置文件 (config.yaml) 中定义。编辑文件并重启服务器以应用更改。",
+  "settings.api_keys.empty": "未配置 API 密钥",
+  "settings.api_keys.load_error": "加载 API 密钥失败",
+  "settings.partial.label": "部分导出 / 导入",
+  "settings.partial.hint": "导出或导入单个实体类型。导入会替换或合并现有数据并重启服务器。",
+  "settings.partial.store.devices": "设备",
+  "settings.partial.store.output_targets": "LED 目标",
+  "settings.partial.store.color_strip_sources": "色带",
+  "settings.partial.store.picture_sources": "图像源",
+  "settings.partial.store.audio_sources": "音频源",
+  "settings.partial.store.audio_templates": "音频模板",
+  "settings.partial.store.capture_templates": "捕获模板",
+  "settings.partial.store.postprocessing_templates": "后处理模板",
+  "settings.partial.store.color_strip_processing_templates": "CSS 处理模板",
+  "settings.partial.store.pattern_templates": "图案模板",
+  "settings.partial.store.value_sources": "值源",
+  "settings.partial.store.sync_clocks": "同步时钟",
+  "settings.partial.store.automations": "自动化",
+  "settings.partial.store.scene_presets": "场景预设",
+  "settings.partial.export_button": "导出",
+  "settings.partial.import_button": "从文件导入",
+  "settings.partial.merge_label": "合并（添加/覆盖，保留现有）",
+  "settings.partial.export_success": "导出成功",
+  "settings.partial.export_error": "导出失败",
+  "settings.partial.import_success": "导入成功",
+  "settings.partial.import_error": "导入失败",
+  "settings.partial.import_confirm_replace": "这将替换所有 {store} 数据并重启服务器。继续吗？",
+  "settings.partial.import_confirm_merge": "这将合并 {store} 数据并重启服务器。继续吗？",
+  "section.empty.devices": "暂无设备。点击 + 添加。",
+  "section.empty.targets": "暂无 LED 目标。点击 + 添加。",
+  "section.empty.kc_targets": "暂无键色目标。点击 + 添加。",
+  "section.empty.pattern_templates": "暂无图案模板。点击 + 添加。",
+  "section.empty.picture_sources": "暂无源。点击 + 添加。",
+  "section.empty.capture_templates": "暂无捕获模板。点击 + 添加。",
+  "section.empty.pp_templates": "暂无后处理模板。点击 + 添加。",
+  "section.empty.audio_sources": "暂无音频源。点击 + 添加。",
+  "section.empty.audio_templates": "暂无音频模板。点击 + 添加。",
+  "section.empty.color_strips": "暂无色带。点击 + 添加。",
+  "section.empty.value_sources": "暂无值源。点击 + 添加。",
+  "section.empty.sync_clocks": "暂无同步时钟。点击 + 添加。",
+  "section.empty.cspt": "暂无 CSS 处理模板。点击 + 添加。",
+  "section.empty.automations": "暂无自动化。点击 + 添加。",
+  "section.empty.scenes": "暂无场景预设。点击 + 添加。"
 }