fix(webapp): keep the clipped queue metric window ordered

A date range that ends before the plan's earliest queryable time had its start
pulled forward past its own end, sending an inverted window to ClickHouse. It
now collapses to an empty window, which is what the enforced lower bound in
executeQuery produces for the same request: no rows.

Author: ericallam

apps/webapp/app/components/queues/queueMetricsPeriod.ts

@@ -97,11 +97,16 @@ export function clampQueueMetricsPeriod(period: string, maxPeriodDays: number):
  * applies to every metric query. Queue-metric queries that go straight to ClickHouse (the queues
  * list table, the concurrency-keys endpoint) have to apply it themselves, otherwise a hand-typed
  * `?period=` reaches further back than the plan allows.
+ *
+ * A range that ends before the plan's earliest queryable time collapses to an empty window rather
+ * than an inverted one, which is what the enforced lower bound in `executeQuery` yields for the
+ * same request: no rows.
  */
 export function clipQueueMetricsWindow(
   window: { from: Date; to: Date },
   maxPeriodDays: number
 ): { from: Date; to: Date } {
   const earliest = new Date(Date.now() - maxPeriodDays * DAY_MS);
-  return { from: window.from < earliest ? earliest : window.from, to: window.to };
+  const from = window.from < earliest ? earliest : window.from;
+  return { from, to: window.to < from ? from : window.to };
 }