feat(water-log): cycle 4 — Tuxedo mobile worker Time tab + unified PIN

The mobile `/water` worker experience (Tuxedo-only, matching the
existing water flow) now exposes a "Time" tab alongside "Headgates"
so irrigators can clock in/out from the same phone they use for
water entries — no second PIN.

- MobileWaterApp: new `activeTab` state, sticky TabBar rendered only
  after PIN, screen='time' case embeds <TimeTrackingFieldClient>
  with hardcoded Tuxedo brand constants.
- handlePinSubmit best-effort calls `verifyTimeTrackingPin` after
  the water PIN succeeds, so the Time tab never re-prompts a worker
  who is also set up in `time_tracking_workers`.
- handleLogout clears BOTH `wl_session` and `time_tracking_session`
  cookies in independent try/catch blocks.
- Tab switching to Time drops in-flight water flow state; switching
  back to Headgates restores the list without reload.
- i18n: added `tab.{headgates,time,logout}` strings (en + es); lifted
  Tuxedo brand display constants into @/lib/water-log/brand so the
  standalone /tuxedo/time-clock page and the embedded Time tab share
  one source of truth.

src/app/tuxedo/time-clock/page.tsx

@@ -1,12 +1,13 @@
 import TimeTrackingFieldClient from "@/components/time-tracking/TimeTrackingFieldClient";
 import { getBrandSettingsPublic } from "@/actions/brand-settings";
-
-const BRAND_ID = "64294306-5f42-463d-a5e8-2ad6c81a96de";
-const BRAND_NAME = "Tuxedo Corn";
-const BRAND_ACCENT = "green";
+import {
+  TUXEDO_BRAND_ID,
+  TUXEDO_BRAND_NAME,
+  TUXEDO_BRAND_ACCENT,
+} from "@/lib/water-log/brand";
 
 export const metadata = {
-  title: "Worker Clock — Tuxedo Corn",
+  title: `Worker Clock — ${TUXEDO_BRAND_NAME}`,
 };
 
 export default async function TuxedoTimeClockPage() {
@@ -15,9 +16,9 @@ export default async function TuxedoTimeClockPage() {
 
   return (
     <TimeTrackingFieldClient
-      brandId={BRAND_ID}
-      brandName={BRAND_NAME}
-      brandAccent={BRAND_ACCENT}
+      brandId={TUXEDO_BRAND_ID}
+      brandName={TUXEDO_BRAND_NAME}
+      brandAccent={TUXEDO_BRAND_ACCENT}
       logoUrl={logoUrl}
     />
   );