Overhaul system health section with job trigger controls and live timestamps

Rebuild the background jobs card as a sortable table showing each job's
schedule, last run time (live-updating via a new useTimeAgo hook), last
duration, and a manual trigger button backed by a new POST
/api/admin/jobs/trigger route. Extract StatusDot into a shared
component. Add cronToHuman() to display schedule patterns as readable
strings (e.g. "Every 6h", "Daily at 03:00"). Replace static
formatDistanceToNow calls throughout the health section with a
LiveTimeAgo component that refreshes every 30 seconds. Also swap a
handful of section icons for better visual matches across settings cards.

app/api/admin/system-health/route.ts

@@ -5,10 +5,12 @@ import { getSystemHealth } from "@/lib/services/system-health";
 
 export async function GET() {
   const session = await auth.api.getSession({ headers: await headers() });
-  if (!session)
+  if (!session) {
     return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
-  if (session.user.role !== "admin")
+  }
+  if (session.user.role !== "admin") {
     return NextResponse.json({ error: "Forbidden" }, { status: 403 });
+  }
 
   const health = await getSystemHealth();
   return NextResponse.json(health);