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/ActiveSessions.tsx

@@ -4,7 +4,7 @@ import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
 import { fetchActiveSessions, reopenBarrier, type ActiveSession } from "./api.js";
 import { qk } from "./lib/query.js";
 import { useShift } from "./lib/use-shift.js";
-import { formatDuration, formatTime } from "./lib/format.js";
+import { formatDuration, formatRelativeDateTime } from "./lib/format.js";
 import { Panel } from "./ui/Panel.js";
 
 // Active Sessions panel. A session is "active" while still inside OR exited-but-
@@ -94,9 +94,7 @@ export function ActiveSessions({ onPick }: { onPick: (identity: string) => void
                   <span className="text-term-text">
                     {s.subscription ? `★ ${s.subscriptionHolder ?? t("subs.unnamed")}` : s.identity}
                   </span>
-                  <span className="text-term-muted">
-                    {t("booth.inAt")} {formatTime(s.enteredAt)}
-                  </span>
+                  <span className="text-term-muted">{formatRelativeDateTime(s.enteredAt, t)}</span>
                   <span className="text-term-muted">{formatDuration(s.enteredAt, new Date().toISOString())}</span>
                   <span className={`ml-auto w-16 text-right font-semibold uppercase ${badge.cls}`}>{t(badge.key)}</span>
                 </button>