fix: Light-Theme-Hintergrund auf PWA/Android reparieren

Der hardcodierte Inline-Style auf body überschrieb --app-body-bg und ließ
hellen Modus mit dunklem Seitenhintergrund erscheinen. Theme-Bootstrap und
dynamisches theme-color ergänzen alle Scheme/Theme-Kombinationen.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/public/appearance-bootstrap.js

@@ -0,0 +1,44 @@
+/**
+ * Applies saved appearance classes before CSS/JS bundle loads (prevents wrong flash on PWA).
+ * Logic mirrors client/src/services/appearance.ts + userPreferences.ts.
+ */
+(function () {
+  try {
+    var uid = localStorage.getItem('active_userid')
+    var theme = 'auto'
+    var scheme = 'auto'
+
+    if (uid) {
+      theme =
+        localStorage.getItem('user_pref_theme_' + uid) ||
+        localStorage.getItem('active_theme') ||
+        'auto'
+      scheme =
+        localStorage.getItem('user_pref_color_scheme_' + uid) ||
+        localStorage.getItem('active_color_scheme') ||
+        'auto'
+    } else {
+      theme = localStorage.getItem('active_theme') || 'auto'
+      scheme = localStorage.getItem('active_color_scheme') || 'auto'
+    }
+
+    var resolvedTheme = theme
+    if (resolvedTheme !== 'ocean' && resolvedTheme !== 'material' && resolvedTheme !== 'cupertino') {
+      var ua = navigator.userAgent || navigator.vendor || ''
+      if (/iPad|iPhone|iPod|Macintosh/.test(ua)) resolvedTheme = 'cupertino'
+      else if (/Android|Linux/.test(ua)) resolvedTheme = 'material'
+      else resolvedTheme = 'ocean'
+    }
+
+    var resolvedScheme = scheme
+    if (resolvedScheme !== 'light' && resolvedScheme !== 'dark') {
+      resolvedScheme = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light'
+    }
+
+    var root = document.documentElement
+    root.classList.add('theme-' + resolvedTheme, 'scheme-' + resolvedScheme)
+    root.style.colorScheme = resolvedScheme
+  } catch (_) {
+    /* ignore storage / matchMedia errors */
+  }
+})()