Wire guest branding theme

resources/js/admin/i18n/locales/en/management.json

@@ -1924,9 +1924,17 @@
       "previewSubtitle": "Current colors & fonts",
       "primary": "Primary",
       "accent": "Accent",
+      "background": "Background",
+      "surface": "Surface",
+      "mode": "Theme",
+      "modeLight": "Light",
+      "modeAuto": "Auto",
+      "modeDark": "Dark",
       "colors": "Colors",
       "primaryColor": "Primary color",
       "accentColor": "Accent color",
+      "backgroundColor": "Background color",
+      "surfaceColor": "Surface color",
       "fonts": "Fonts",
       "headingFont": "Headline font",
       "headingFontPlaceholder": "SF Pro Display",