fix: refactor time range to single source of truth with correct dates

- Default range changed from 30d to 7d
- Presets (today/7d/30d) now directly set customStart/customEnd dates,
  eliminating duplicate getTimeRange() calculation
- "All" preset fetches actual data boundaries from /api/date-range
  and backfills the custom date picker
- Clicking "custom" opens popover without triggering data refresh;
  only confirm applies changes
- SQL trend dates cast to ::text to avoid pg driver Date timezone offset
- Fix created_at filter from < to <= for end timestamp

app/api/date-range/route.ts

@@ -0,0 +1,7 @@
+import { NextResponse } from "next/server";
+import { getDateRange } from "@/lib/queries";
+
+export async function GET() {
+  const data = await getDateRange();
+  return NextResponse.json(data);
+}