Polish settings UI, add tooltips, replace timeAgo with date-fns

Clean up settings section design: consolidate backup cards, add
hover-reveal actions with tooltips, improve icon sizing across
components, and replace custom timeAgo helper with date-fns
formatDistanceToNow in webhook card.

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

app/(pages)/settings/_components/server-section.tsx

@@ -37,7 +37,7 @@ export function ServerSection({
       <div className="flex items-center justify-between gap-4">
         <div className="flex items-start gap-3">
           <div className="mt-0.5 flex h-8 w-8 shrink-0 items-center justify-center rounded-lg bg-primary/10">
-            <IconUserPlus size={16} className="text-primary" />
+            <IconUserPlus className="size-4 text-primary" />
           </div>
           <div>
             <CardTitle>Open registration</CardTitle>