chore: rebrand DC Automod to Discord Automod across UI

Updates the page title metadata, sidebar brand text, and settings page
about section from "DC Automod" to "Discord Automod".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

services/frontend/src/components/layout/app-sidebar.tsx

@@ -39,7 +39,7 @@ export function AppSidebar() {
         </div>
         <div>
           <div className="text-sm font-bold tracking-tight">
-            <span className="text-gradient">DC Automod</span>
+            <span className="text-gradient">Discord Automod</span>
           </div>
           <div className="text-[10px] text-muted-foreground tracking-widest uppercase leading-none">
             Dashboard