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/lib/format.ts

@@ -28,3 +28,58 @@ export function formatTime(iso: string | null): string {
   const d = new Date(iso);
   return Number.isNaN(d.getTime()) ? "—" : d.toTimeString().slice(0, 8);
 }
+
+/** Calendar-day difference (local) between two dates: 0 = same day, 1 = d is one day
+ *  before ref, etc. Compares date parts only (ignores time-of-day). */
+function dayDiff(d: Date, ref: Date): number {
+  const a = new Date(d.getFullYear(), d.getMonth(), d.getDate());
+  const b = new Date(ref.getFullYear(), ref.getMonth(), ref.getDate());
+  return Math.round((b.getTime() - a.getTime()) / 86_400_000);
+}
+
+/** HH:MM (local, 24h) for the relative-day labels. */
+function hhmm(d: Date): string {
+  const p = (n: number) => String(n).padStart(2, "0");
+  return `${p(d.getHours())}:${p(d.getMinutes())}`;
+}
+
+/** Minimal shape of i18next's `t` that we rely on: a string lookup, plus the
+ *  `returnObjects` overload used to fetch the month-name array. */
+export interface TFn {
+  (key: string): string;
+  (key: string, opts: { returnObjects: true }): unknown;
+}
+
+/** Localized month name (index 0 = January) from the i18n catalog. Browser ICU on
+ *  the appliance may lack Albanian data, so we DON'T use Intl — the catalog is the
+ *  source of truth. Falls back to a numeric month if the array is missing. */
+function monthName(d: Date, t: TFn): string {
+  const months = t("common.months", { returnObjects: true });
+  if (Array.isArray(months) && typeof months[d.getMonth()] === "string") {
+    return months[d.getMonth()] as string;
+  }
+  return String(d.getMonth() + 1);
+}
+
+/**
+ * Human, day-relative date+time for sessions/logs/history. An event from earlier
+ * today reads "Sot 10:48", yesterday "Dje 17:33", and anything older a localized
+ * "17 Qershor 10:48" (month name from the active catalog). Keeps time-of-day on
+ * every variant — operators care about it within a shift.
+ *
+ * `t` supplies the today/yesterday words AND the month names (the appliance browser
+ * may lack Albanian Intl data, so month names come from the catalog, not Intl).
+ */
+export function formatRelativeDateTime(iso: string | null, t: TFn): string {
+  if (!iso) return "—";
+  const d = new Date(iso);
+  if (Number.isNaN(d.getTime())) return "—";
+  const diff = dayDiff(d, new Date());
+  if (diff === 0) return `${t("common.today")} ${hhmm(d)}`;
+  if (diff === 1) return `${t("common.yesterday")} ${hhmm(d)}`;
+  // Older (or future): "17 Qershor 10:48", with the year only if it differs.
+  const sameYear = d.getFullYear() === new Date().getFullYear();
+  const month = monthName(d, t);
+  const date = sameYear ? `${d.getDate()} ${month}` : `${d.getDate()} ${month} ${d.getFullYear()}`;
+  return `${date} ${hhmm(d)}`;
+}