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/router.tsx

@@ -99,10 +99,17 @@ function LanguageToggle({
   user: SessionUser;
   setUser: (u: SessionUser | null) => void;
 }) {
+  // The ACTIVE language is i18n's own state, not the router-context `user` — the
+  // latter is captured at route-resolution time and does NOT re-render when we call
+  // setUser, so reading `user.language` here goes stale after the first switch (the
+  // highlight froze and the equality guard blocked switching back until a refresh).
+  // useTranslation() subscribes to i18n's languageChanged, so this stays live.
+  const { i18n } = useTranslation();
+  const active = i18n.language as Lang;
   async function pick(lang: Lang) {
-    if (lang === user.language) return;
-    setLanguage(lang); // instant UI
-    setUser({ ...user, language: lang });
+    if (lang === active) return;
+    setLanguage(lang); // instant UI (fires i18n languageChanged → re-render)
+    setUser({ ...user, language: lang }); // keep context eventually-consistent + persisted state
     try {
       await setLanguagePref(lang); // persist
     } catch {
@@ -117,7 +124,7 @@ function LanguageToggle({
           type="button"
           onClick={() => pick(l)}
           className={`rounded-term px-1.5 py-0.5 ${
-            user.language === l ? "bg-term-panel-2 text-term-amber" : "text-term-muted hover:text-term-text"
+            active === l ? "bg-term-panel-2 text-term-amber" : "text-term-muted hover:text-term-text"
           }`}
         >
           {l}
@@ -138,10 +145,17 @@ function ThemeToggle({
   setUser: (u: SessionUser | null) => void;
 }) {
   const { t } = useTranslation();
+  // Local state for the ACTIVE theme — same reason as LanguageToggle: the router
+  // context `user` doesn't re-render on setUser, so reading `user.theme` here froze
+  // the highlight after one switch and blocked toggling back until a refresh. Seed
+  // from the prop; update optimistically on pick. App's effect keeps the DOM in sync
+  // with the persisted user on (re)login.
+  const [active, setActive] = useState<Theme>(user.theme);
   async function pick(theme: Theme) {
-    if (theme === user.theme) return;
+    if (theme === active) return;
+    setActive(theme);
     applyTheme(theme); // instant UI
-    setUser({ ...user, theme });
+    setUser({ ...user, theme }); // keep context eventually-consistent + persisted state
     try {
       await setThemePref(theme); // persist
     } catch {
@@ -156,7 +170,7 @@ function ThemeToggle({
           type="button"
           onClick={() => pick(th)}
           className={`rounded-term px-1.5 py-0.5 ${
-            user.theme === th ? "bg-term-panel-2 text-term-amber" : "text-term-muted hover:text-term-text"
+            active === th ? "bg-term-panel-2 text-term-amber" : "text-term-muted hover:text-term-text"
           }`}
         >
           {t(th === "dark" ? "common.themeDark" : "common.themeLight")}