fix(ai): count the daily AI budget on the account's own day

The token ledger keyed every day on UTC while the daily briefing and the
other per-day generations run on the account's local day, so east of UTC
the first generations after local midnight were refused against the
previous day's spent ceiling. The budget day is now the calendar day in
the account's time zone; each request still resolves it once and books
its reservation and reconcile on the same row. The medication extraction
reads relative phrases against the same local day, the operator's spend
card shows the operator's own day, and the limit copy says the budget
resets at midnight in the person's time zone.

src/app/api/admin/provider-health/route.ts

@@ -73,11 +73,13 @@ interface ProviderHealthSummary {
 const CENTRAL_TYPES = [...OPERATOR_HELD_PROVIDER_TYPES];
 
 export const GET = apiHandler(async () => {
-  await requireAdmin();
+  const { user } = await requireAdmin();
   annotate({ action: { name: "admin.provider-health.get" } });
 
-  // The UTC day the ledger buckets by — the same key every reservation writes.
-  const dateKey = buildDateKey();
+  // The ledger buckets each account by its own local day; the operator's
+  // "today" is the day in the operator's own zone, which on a single-zone
+  // instance is everyone's.
+  const dateKey = await buildDateKey(user.id);
 
   const groups = await prisma.providerHealth.groupBy({
     // `lastStatus` joins the grouping key rather than an aggregate: the