Add interactive getting-started tutorial for first-time users

Auto-starts on first visit with a 9-step walkthrough covering header,
tabs, settings, search, theme, and language controls. Stores completion
in localStorage; restart via ? button in the header. Includes en/ru/zh
translations for all tour steps.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/wled_controller/static/locales/zh.json

@@ -214,6 +214,16 @@
   "calibration.tip.border_width": "从屏幕边缘采样多少像素来确定 LED 颜色",
   "calibration.tip.skip_leds_start": "跳过灯带起始端的 LED — 被跳过的 LED 保持关闭",
   "calibration.tip.skip_leds_end": "跳过灯带末尾端的 LED — 被跳过的 LED 保持关闭",
+  "tour.welcome": "欢迎使用 LED Grab！快速导览将带您了解界面。使用方向键或按钮进行导航。",
+  "tour.dashboard": "仪表盘 — 实时查看运行中的目标、配置文件和设备状态。",
+  "tour.targets": "目标 — 添加 WLED 设备，配置 LED 目标的捕获设置和校准。",
+  "tour.sources": "来源 — 管理捕获模板、图片来源、音频来源和色带。",
+  "tour.profiles": "配置文件 — 将目标分组，并通过时间、音频或数值条件自动切换。",
+  "tour.settings": "设置 — 备份和恢复配置，管理自动备份。",
+  "tour.search": "搜索 — 使用 Ctrl+K 快速查找并导航到任意实体。",
+  "tour.theme": "主题 — 在深色和浅色模式之间切换。",
+  "tour.language": "语言 — 选择您偏好的界面语言。",
+  "tour.restart": "重新开始导览",
   "calibration.tutorial.start": "开始教程",
   "calibration.overlay_toggle": "叠加层",
   "calibration.start_position": "起始位置：",