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/js/app.js

@@ -22,7 +22,7 @@ import {
     openDisplayPicker, closeDisplayPicker, selectDisplay, formatDisplayLabel,
 } from './features/displays.js';
 import {
-    startCalibrationTutorial, startDeviceTutorial,
+    startCalibrationTutorial, startDeviceTutorial, startGettingStartedTutorial,
     closeTutorial, tutorialNext, tutorialPrev,
 } from './features/tutorials.js';
 
@@ -174,6 +174,7 @@ Object.assign(window, {
     // tutorials
     startCalibrationTutorial,
     startDeviceTutorial,
+    startGettingStartedTutorial,
     closeTutorial,
     tutorialNext,
     tutorialPrev,
@@ -502,4 +503,9 @@ document.addEventListener('DOMContentLoaded', async () => {
     // Start global events WebSocket and auto-refresh
     startEventsWS();
     startAutoRefresh();
+
+    // Show getting-started tutorial on first visit
+    if (!localStorage.getItem('tour_completed')) {
+        setTimeout(() => startGettingStartedTutorial(), 600);
+    }
 });