fix(admin): bump UI stale threshold 60/90s -> 300s

The 'stale' badge in /admin/scrape/* tables was a UI-only label
computed as Date.now() - heartbeat_at > 60s (90s for geo). Heartbeats
naturally lag past 60s during WAF backoff (30s) or NSPD HTTP timeout
(15s) — every page render flashed running jobs as 'stale' even though
they were processing.

300s threshold matches the real auto-resume threshold in the worker
(jobs are zombies only after >5 min of silence). Less false-positive
churn in the UI.

frontend/src/app/admin/scrape/all/page.tsx

@@ -231,7 +231,7 @@ export default function ScrapeAllAdminPage() {
                 const isStale =
                   r.status === "running" &&
                   heartbeatLag !== null &&
-                  heartbeatLag > 60;
+                  heartbeatLag > 300;
                 const badge = SCRAPER_BADGE[r.scraper_type];
                 const statusColor = STATUS_COLOR[r.status] ?? "#6b7280";
                 return (

frontend/src/app/admin/scrape/geo/page.tsx

@@ -361,7 +361,7 @@ export default function GeoScrapeAdminPage() {
                 const isStale =
                   j.status === "running" &&
                   heartbeatLag !== null &&
-                  heartbeatLag > 90;
+                  heartbeatLag > 300;
                 const color = STATUS_COLOR[j.status] ?? "#6b7280";
                 return (
                   <tr key={j.job_id} style={{ borderTop: "1px solid #f3f4f6" }}>

frontend/src/app/admin/scrape/objective/page.tsx

@@ -694,7 +694,7 @@ export default function ObjectiveEtlAdminPage() {
                 const isStale =
                   r.status === "running" &&
                   heartbeatLag !== null &&
-                  heartbeatLag > 60;
+                  heartbeatLag > 300;
                 const statusColor =
                   r.status === "done"
                     ? "#16a34a"