Auto-recheck parity after scrape + manual Recheck button + faster badge

Parity logic:
- Extract _fetch_latest_alerts() and _upsert_alerts() helpers so the alert
  upsert loop is no longer duplicated between the daily job and per-date runs
- Add run_parity_check_for_date(date) which runs the full comparison +
  alert upsert for a single date

Scraper integration:
- _safe_parity_recheck(date) wrapper (never raises) called after each
  successful date in both search-results and hotel-page workers; hotel-page
  mode waits until all hotels for the date are done before rechecking

API:
- POST /competitors/parity/check-date?rate_date=YYYY-MM-DD for manual recheck

Frontend:
- Recheck button on every parity alert row (all statuses); invalidates
  alerts list and badge count on success
- parity-alert-count badge polls every 15s (was 60s) so new alerts from
  the scheduled job or post-scrape rechecks appear quickly

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/Layout.tsx

@@ -23,7 +23,7 @@ export default function Layout({ children }: { children: ReactNode }) {
   const { data: alertCount } = useQuery<number>({
     queryKey: ['parity-alert-count'],
     queryFn: () => api.get('/competitors/parity/alerts?status=active').then(r => r.data.length),
-    refetchInterval: 60_000,
+    refetchInterval: 15_000,
     enabled: can(user, 'view_competitors'),
   })
 

frontend/src/pages/MarketView.tsx

@@ -843,6 +843,15 @@ const ParityAlertsTab: React.FC = () => {
     },
   })
 
+  const recheckMutation = useMutation({
+    mutationFn: async (rateDate: string) =>
+      (await api.post(`/competitors/parity/check-date?rate_date=${rateDate}`)).data,
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['parity-alerts'] })
+      queryClient.invalidateQueries({ queryKey: ['parity-alert-count'] })
+    },
+  })
+
   const markupUnit = parityConfig?.['parity_markup_unit'] ?? 'pct'
   const toleranceUnit = parityConfig?.['parity_tolerance_unit'] ?? 'pct'
   const markupVal = parityConfig?.['parity_markup_value'] ?? parityConfig?.['parity_expected_markup_pct'] ?? '0'
@@ -945,19 +954,29 @@ const ParityAlertsTab: React.FC = () => {
                       {a.alert_status}
                     </span>
                   </td>
-                  <td style={tdStyle}>
-                    {a.alert_status === 'active' && (
+                  <td style={mergeStyles(tdStyle, { whiteSpace: 'nowrap' })}>
+                    <div style={{ display: 'flex', gap: 6, alignItems: 'center' }}>
+                      {a.alert_status === 'active' && (
+                        <button
+                          style={buttonStyle('outline', 'small')}
+                          disabled={ackMutation.isPending || recheckMutation.isPending}
+                          onClick={() => ackMutation.mutate(a.id)}
+                        >
+                          Acknowledge
+                        </button>
+                      )}
                       <button
                         style={buttonStyle('outline', 'small')}
-                        disabled={ackMutation.isPending}
-                        onClick={() => ackMutation.mutate(a.id)}
+                        disabled={recheckMutation.isPending || ackMutation.isPending}
+                        onClick={() => recheckMutation.mutate(a.rate_date)}
+                        title="Re-run parity check using the latest scraped rates for this date"
                       >
-                        Acknowledge
+                        Recheck
                       </button>
-                    )}
-                    {a.alert_status === 'acknowledged' && a.acknowledged_by && (
-                      <span style={{ fontSize: 11, color: 'var(--text-mid)' }}>by {a.acknowledged_by}</span>
-                    )}
+                      {a.alert_status === 'acknowledged' && a.acknowledged_by && (
+                        <span style={{ fontSize: 11, color: 'var(--text-mid)' }}>by {a.acknowledged_by}</span>
+                      )}
+                    </div>
                   </td>
                 </tr>
               ))}