fix: period end date set to yesterday and show fertile range during ongoing period

Clicking "Period Ended" now records yesterday as the end date, since
you only know the period ended the day after. Also added the missing
fertile date range to the ongoing-period status view.

src/lib/components/fitness/PeriodTracker.svelte

@@ -444,7 +444,7 @@
 			const res = await fetch(`/api/fitness/period/${ongoing._id}`, {
 				method: 'PUT',
 				headers: { 'Content-Type': 'application/json' },
-				body: JSON.stringify({ endDate: new Date().toISOString() })
+				body: JSON.stringify({ endDate: new Date(Date.now() - 86400000).toISOString() })
 			});
 			if (res.ok) {
 				const { entry } = await res.json();
@@ -606,6 +606,10 @@
 							<span class="status-side-relative">{relativeDate(nextCycle.fertileEnd)}</span>
 							<span class="status-side-date">{formatDate(nextCycle.fertileEnd)}</span>
 						</div>
+						<div class="status-side-item fertile-accent">
+							<span class="status-side-label">{t('fertile', lang)}</span>
+							<span class="status-side-date">{formatDate(nextCycle.fertileStart)} — {formatDate(nextCycle.fertileEnd)}</span>
+						</div>
 					</div>
 				{/if}
 			</div>