feat(web): i18n with react-i18next — Albanian default, English second

Add react-i18next with two key-parity-checked catalogs (sq default/fallback, en).
Active language driven by the logged-in user's stored preference (applied after
/me resolves); SQ/EN toggle in the header persists via PUT /api/auth/language.
Translate the booth (screen, pay/exit modal, active sessions, snapshots, status),
Login, ShiftControl, SiteSettings, PermitManager, TariffComposer.

SetupWizard deferred (its content is server-provided; needs backend catalog i18n).

apps/web/src/Login.tsx

@@ -1,7 +1,9 @@
 import { useState } from "react";
+import { useTranslation } from "react-i18next";
 import { login, type SessionUser } from "./api.js";
 
 export function Login({ onLoggedIn }: { onLoggedIn: (u: SessionUser) => void }) {
+  const { t } = useTranslation();
   const [username, setUsername] = useState("");
   const [password, setPassword] = useState("");
   const [error, setError] = useState<string | null>(null);
@@ -22,11 +24,11 @@ export function Login({ onLoggedIn }: { onLoggedIn: (u: SessionUser) => void })
 
   return (
     <main style={{ fontFamily: "system-ui", maxWidth: 320, margin: "4rem auto" }}>
-      <h1>Parking System</h1>
+      <h1>{t("auth.title")}</h1>
       <form onSubmit={submit}>
         <div style={{ margin: "0.5rem 0" }}>
           <label>
-            Username
+            {t("auth.username")}
             <br />
             <input
               value={username}
@@ -39,7 +41,7 @@ export function Login({ onLoggedIn }: { onLoggedIn: (u: SessionUser) => void })
         </div>
         <div style={{ margin: "0.5rem 0" }}>
           <label>
-            Password
+            {t("auth.password")}
             <br />
             <input
               type="password"
@@ -52,7 +54,7 @@ export function Login({ onLoggedIn }: { onLoggedIn: (u: SessionUser) => void })
         </div>
         {error && <p style={{ color: "crimson" }}>{error}</p>}
         <button type="submit" disabled={busy || !username || !password}>
-          {busy ? "Signing in…" : "Sign in"}
+          {busy ? t("auth.signingIn") : t("auth.signIn")}
         </button>
       </form>
     </main>