feat(alerts): always-visible dismiss/ack actions + Dismiss all (service, endpoint, UI)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/components/alerts/alert-card.tsx

@@ -62,7 +62,7 @@ export function AlertCard({ alert, readOnly = false }: AlertCardProps) {
         </div>
       </div>
       {!readOnly ? (
-        <div className="flex shrink-0 items-start gap-1 opacity-0 transition-opacity duration-base ease-spring group-hover:opacity-100 focus-within:opacity-100">
+        <div className="flex shrink-0 items-start gap-1 text-muted-foreground">
           {!acknowledged ? (
             <Button
               variant="ghost"