Fix repeater clock drift-drift on nav-away-come-back

frontend/src/components/repeater/RepeaterNodeInfoPane.tsx

@@ -16,8 +16,8 @@ export function NodeInfoPane({
 }) {
   const clockDrift = useMemo(() => {
     if (!data?.clock_utc) return null;
-    return formatClockDrift(data.clock_utc);
-  }, [data?.clock_utc]);
+    return formatClockDrift(data.clock_utc, state.fetched_at ?? undefined);
+  }, [data?.clock_utc, state.fetched_at]);
 
   return (
     <RepeaterPane title="Node Info" state={state} onRefresh={onRefresh} disabled={disabled}>

frontend/src/components/repeater/repeaterPaneShared.tsx

@@ -39,7 +39,10 @@ export function formatDuration(seconds: number): string {
   return `${mins}m`;
 }
 
-export function formatClockDrift(clockUtc: string): { text: string; isLarge: boolean } {
+export function formatClockDrift(
+  clockUtc: string,
+  referenceTimeMs: number = Date.now()
+): { text: string; isLarge: boolean } {
   // Firmware format: "HH:MM - D/M/YYYY UTC" or "HH:MM:SS - D/M/YYYY UTC"
   // Also handle ISO-like: "YYYY-MM-DD HH:MM:SS"
   let parsed: Date;
@@ -56,7 +59,7 @@ export function formatClockDrift(clockUtc: string): { text: string; isLarge: boo
   }
   if (isNaN(parsed.getTime())) return { text: '(invalid)', isLarge: false };
 
-  const driftMs = Math.abs(Date.now() - parsed.getTime());
+  const driftMs = Math.abs(referenceTimeMs - parsed.getTime());
   const driftSec = Math.floor(driftMs / 1000);
 
   if (driftSec >= 86400) return { text: '>24 hours!', isLarge: true };

frontend/src/test/repeaterDashboard.test.tsx

@@ -401,6 +401,40 @@ describe('RepeaterDashboard', () => {
     expect(screen.getByText(/Fetched .*Just now/)).toBeInTheDocument();
   });
 
+  it('keeps repeater clock drift anchored to fetch time across remounts', () => {
+    vi.useFakeTimers();
+    try {
+      const fetchedAt = Date.UTC(2024, 0, 1, 12, 0, 0);
+      vi.setSystemTime(fetchedAt);
+
+      mockHook.loggedIn = true;
+      mockHook.paneData.nodeInfo = {
+        name: 'TestRepeater',
+        lat: null,
+        lon: null,
+        clock_utc: '11:59:30 - 1/1/2024 UTC',
+      };
+      mockHook.paneStates.nodeInfo = {
+        loading: false,
+        attempt: 1,
+        error: null,
+        fetched_at: fetchedAt,
+      };
+
+      const firstRender = render(<RepeaterDashboard {...defaultProps} />);
+      expect(screen.getByText(/\(drift: 30s\)/)).toBeInTheDocument();
+
+      vi.setSystemTime(fetchedAt + 10 * 60 * 1000);
+      firstRender.unmount();
+
+      render(<RepeaterDashboard {...defaultProps} />);
+      expect(screen.getByText(/\(drift: 30s\)/)).toBeInTheDocument();
+      expect(screen.queryByText(/\(drift: 10m30s\)/)).not.toBeInTheDocument();
+    } finally {
+      vi.useRealTimers();
+    }
+  });
+
   it('renders action buttons', () => {
     mockHook.loggedIn = true;