chore(brand): surface ccswitch.io as the sole official website

Add an "Only Official Website" header to the three READMEs, an
About panel button, and a tray menu entry — all pointing to
ccswitch.io. Consolidates brand and SEO signals on the canonical
domain across docs, GUI, and system tray.

src/components/settings/AboutSection.tsx

@@ -3,6 +3,7 @@ import {
   Download,
   Copy,
   ExternalLink,
+  Globe,
   Info,
   Loader2,
   RefreshCw,
@@ -360,6 +361,16 @@ export function AboutSection({ isPortable }: AboutSectionProps) {
           </div>
 
           <div className="flex items-center gap-2">
+            <Button
+              type="button"
+              variant="outline"
+              size="sm"
+              onClick={() => settingsApi.openExternal("https://ccswitch.io")}
+              className="h-8 gap-1.5 text-xs"
+            >
+              <Globe className="h-3.5 w-3.5" />
+              {t("settings.officialWebsite")}
+            </Button>
             <Button
               type="button"
               variant="outline"