Add build date and time to system update information

Update admin panel to display build stamp and started at timestamps, fixing `data.current.build` and `data.startedAt` formatting.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 77cfe984-2c65-4152-bb7a-0df28274fe66
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: 4b47ebeb-8643-405e-b1c8-6d9320ea2345
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/c3c252e4-c83d-40ca-9fff-99a3ea60701e/77cfe984-2c65-4152-bb7a-0df28274fe66/m92e9kU
Replit-Helium-Checkpoint-Created: true

artifacts/tx-os/src/pages/admin.tsx

@@ -2499,11 +2499,14 @@ function SystemUpdatesPanel() {
                 <span className="tabular-nums" data-testid="system-updates-current-build">
                   {data.current.build}
                 </span>
-                {formatBuildStamp(data.current.build) && (
-                  <span className="ms-2 text-muted-foreground/80">
-                    ({formatBuildStamp(data.current.build)})
-                  </span>
-                )}
+                {(() => {
+                  const human = formatBuildStamp(data.current.build);
+                  return human ? (
+                    <span className="ms-2 text-muted-foreground/80">
+                      ({human})
+                    </span>
+                  ) : null;
+                })()}
               </div>
               {data.startedAt && (
                 <div
@@ -2514,7 +2517,7 @@ function SystemUpdatesPanel() {
                   {formatChecked(
                     typeof data.startedAt === "string"
                       ? data.startedAt
-                      : (data.startedAt as Date).toISOString(),
+                      : data.startedAt.toISOString(),
                   )}
                 </div>
               )}