fix: show live delta in closed-week banner instead of stale frozen value

closedWeek.delta_ms is a snapshot taken at close time and goes stale
if entries are edited or days are re-closed afterward. The summary
rows above already use the live totalWorkedMs - expectedMs; the
closed-week banner now uses the same expression.

web/src/routes/week/+page.svelte

@@ -141,7 +141,7 @@
 
 	{#if closedWeek}
 		<div class="week-closed">
-			<p>Week closed — overtime: <strong>{formatDelta(closedWeek.delta_ms)}</strong></p>
+			<p>Week closed — overtime: <strong>{formatDelta(totalWorkedMs - expectedMs)}</strong></p>
 			<button onclick={handleReopenWeek}>Reopen week</button>
 		</div>
 	{:else if canCloseWeek}