feat: human + relative dates; fix language/theme toggle stale-context

Dates were raw ISO on printed slips and time-only in the UI (a session from
two days ago showed just "10:48"). Make them human and day-relative. Also fix
a latent toggle bug surfaced while testing.

Dates:
- Printed tickets/receipts/subscription cards now show "19 Qershor 2026
  10:48:25" (Albanian month, 24h with seconds) instead of YYYY-MM-DD HH:MM.
  stamp() exported as formatStampSq so the shift Z-report shares it.
- Shift Z-report is now Albanian (Operatori/Nga/Deri/Para në dorë/Arka…),
  was English-only with ISO dates.
- Web sessions/logs/history show relative days: "Sot 10:48" / "Dje 17:33" /
  "17 Qershor 10:48" via formatRelativeDateTime(). Month names come from the
  i18n catalog (common.months), NOT Intl — the appliance browser's ICU lacks
  Albanian locale data and Intl silently falls back to English month names.

Toggle fix:
- The language + theme toggles read the active value from the TanStack Router
  context `user`, which is captured at route-resolution time and does not
  re-render on setUser. After one switch the highlight froze and the equality
  guard blocked switching back until a page refresh. Drive them off live state
  instead: language from i18n.language (useTranslation subscribes to
  languageChanged), theme from local useState. (Bug dated to 040c0ff.)

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/BoothPayModal.tsx

@@ -15,7 +15,7 @@ import {
 } from "./api.js";
 import { qk } from "./lib/query.js";
 import { useShift } from "./lib/use-shift.js";
-import { formatDuration, formatMoney, formatTime } from "./lib/format.js";
+import { formatDuration, formatMoney, formatTime, formatRelativeDateTime } from "./lib/format.js";
 import { SnapshotStrip } from "./ui/SnapshotStrip.js";
 
 // The booth pay/exit modal. Opened when the operator submits a ticket id. Shows the
@@ -213,7 +213,7 @@ export function BoothPayModal({ identity, onClose }: { identity: string; onClose
               <>
                 {/* Session figures */}
                 <div className="grid grid-cols-2 gap-x-6 gap-y-1 tabular-nums">
-                  <Row label={t("pay.entry")} value={formatTime(s.enteredAt)} />
+                  <Row label={t("pay.entry")} value={formatRelativeDateTime(s.enteredAt, t)} />
                   <Row label={t("pay.now")} value={formatTime(new Date().toISOString())} />
                   <Row
                     label={t("pay.duration")}