fix(auth): redirect already-signed-in users away from the login page

Visiting /login while authenticated now redirects to the app (/pos) instead of
showing the login form again. Guarded on _hasHydrated so the not-yet-rehydrated
(null) session isn't misread, and renders a brief "redirecting" state instead of
flashing the form. fa/en/ar strings added.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

web/dashboard/messages/ar.json

@@ -39,6 +39,7 @@
   "auth": {
     "title": "تسجيل الدخول إلى ميزي",
     "subtitle": "سيتم إرسال رمز التحقق إلى هاتفك",
+    "redirecting": "مسجّل الدخول بالفعل — يتم التحويل…",
     "phone": "رقم الجوال",
     "phonePlaceholder": "٠٩١٢١٢٣٤٥٦٧",
     "sendOtp": "إرسال الرمز",

web/dashboard/messages/en.json

@@ -39,6 +39,7 @@
   "auth": {
     "title": "Sign in to Meezi",
     "subtitle": "We will send a verification code to your phone",
+    "redirecting": "Already signed in — redirecting…",
     "phone": "Mobile number",
     "phonePlaceholder": "09121234567",
     "sendOtp": "Send code",

web/dashboard/messages/fa.json

@@ -39,6 +39,7 @@
   "auth": {
     "title": "ورود به میزی",
     "subtitle": "کد تأیید به موبایل شما ارسال می‌شود",
+    "redirecting": "قبلاً وارد شده‌اید — در حال انتقال…",
     "phone": "شماره موبایل",
     "phonePlaceholder": "۰۹۱۲۱۲۳۴۵۶۷",
     "sendOtp": "ارسال کد",