feat(water-log): cycle 3 — embed Time Tracking tab in admin shell

The water-log admin panel at /admin/water-log becomes a one-stop hub for
the customer: today's entries, the headgates, who can log them, AND how
many hours those workers put in.

- New TimeTrackingTab — thin wrapper that renders the existing
  TimeTrackingAdminPanel (which already owns its own Summary / Workers
  / Tasks / Logs / Settings sub-tabs).
- Shell.tsx now exposes Today | Headgates | Users | Time Tracking; the
  new branch just passes brandId through.
- TabValue union and TABS[] updated to "time-tracking".

This is the customer-facing surface the user asked for. Cycle 4 adds
the same tab to the mobile worker portal; Cycle 5 scaffolds the
Smartsheet sync (config-deferred).

src/components/admin/water-log/tabs/TimeTrackingTab.tsx

@@ -0,0 +1,18 @@
+/**
+ * Time Tracking tab — embeds the existing TimeTrackingAdminPanel
+ * (which already has its own sub-tabs: Summary / Workers / Tasks /
+ * Logs / Settings) inside the Water Log shell.
+ *
+ * Cycle 3 — this is the customer "hub" surface the water log now
+ * offers: one place to see today's entries, the headgates, who can
+ * log them, AND how many hours those workers put in.
+ */
+import TimeTrackingAdminPanel from "@/components/admin/TimeTrackingAdminPanel";
+
+export type TimeTrackingTabProps = {
+  brandId: string;
+};
+
+export function TimeTrackingTab({ brandId }: TimeTrackingTabProps) {
+  return <TimeTrackingAdminPanel brandId={brandId} />;
+}