Make onboarding tour install-wide instead of per-browser

Persist onboardingCompleted flag server-side via /api/v1/config so the
tour only auto-starts once per DashCaddy installation, not on every
new browser that connects.

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

status/js/onboarding.js

@@ -22,6 +22,12 @@
     try {
       console.log('[Onboarding] Initializing system...');
 
+      if (window.__dashcaddySiteConfigLoaded) {
+        try {
+          await window.__dashcaddySiteConfigLoaded;
+        } catch (_) { /* ignore */ }
+      }
+
       // Initialize Error Handler first
       errorHandler = new ErrorHandler();
       console.log('[Onboarding] Error Handler initialized');
@@ -44,7 +50,8 @@
 
       // Check if tour should auto-start
       if (tourManager.shouldAutoStart()) {
-        console.log('[Onboarding] Auto-starting tour for first-time user');
+        console.log('[Onboarding] Auto-starting tour for first-time install');
+        await progressTracker.markInstallOnboardingCompleted();
         // Wait a bit for page to fully load
         setTimeout(() => {
           tourManager.startTour();