feat(kayıt): yeni hane kaydı yalnızca davetle (REGISTRATION=invite_only)

- REGISTRATION ortam değişkeni: invite_only (varsayılan) | open
- invite_only: ilk hane serbest, sonrasında yalnızca davet koduyla katılım
- Backend'de zorunlu: 403 registration_closed; GET /api/auth/registration
- Kayıt ekranı: kayıt kapalıyken yalnızca davet kodu ve açıklama
- Entegrasyon testleri: kayıt politikası (2)
- Prettier ayarı eklendi (proje stiliyle uyumlu), kaynaklar biçimlendirildi

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/features/auth/register-page.tsx

@@ -1,5 +1,7 @@
 import { zodResolver } from '@hookform/resolvers/zod'
-import { Home, Loader2, UserPlus, Users } from 'lucide-react'
+import { useEffect } from 'react'
+import { useQuery, useQueryClient } from '@tanstack/react-query'
+import { Home, Info, Loader2, UserPlus, Users } from 'lucide-react'
 import { Controller, useForm, useWatch } from 'react-hook-form'
 import { Link, useSearchParams } from 'react-router'
 import { toast } from 'sonner'
@@ -7,11 +9,13 @@ import { FormError, FormField, PasswordInput } from '@/components/form-field'
 import { paths } from '@/components/layout/nav-items'
 import { Button } from '@/components/ui/button'
 import { Input } from '@/components/ui/input'
-import { ApiError } from '@/lib/api'
+import { api, ApiError } from '@/lib/api'
 import { useRegister } from '@/lib/auth'
+import { queryKeys } from '@/lib/query'
 import { t } from '@/lib/strings'
 import { cn } from '@/lib/utils'
 import { AuthShell } from './auth-shell'
+import type { RegistrationInfo } from '@/types/RegistrationInfo'
 import { normalizeInviteCode, registerSchema, type RegisterForm } from './schemas'
 
 const s = t.auth.register
@@ -22,11 +26,20 @@ export function RegisterPage() {
   // Davet bağlantısı: /kayit?davet=ABCD-EFGH → "Davetle katıl" seçili ve kod dolu
   const invite = params.get('davet') ?? ''
 
+  // Sunucu politikası (REGISTRATION): yeni hane kurulabilir mi?
+  const qc = useQueryClient()
+  const info = useQuery({
+    queryKey: queryKeys.registration,
+    queryFn: () => api.get<RegistrationInfo>('/auth/registration'),
+  })
+  const newAllowed = info.data?.new_household_allowed ?? true
+
   const {
     register,
     control,
     handleSubmit,
     setError,
+    setValue,
     formState: { errors, isSubmitting },
   } = useForm<RegisterForm>({
     resolver: zodResolver(registerSchema),
@@ -40,6 +53,11 @@ export function RegisterPage() {
       invite_code: invite,
     },
   })
+  // Kayıt kapalıysa yalnızca "Davetle katıl"
+  useEffect(() => {
+    if (!newAllowed) setValue('mode', 'join')
+  }, [newAllowed, setValue])
+
   const mode = useWatch({ control, name: 'mode' })
   const name = useWatch({ control, name: 'name' }).trim()
 
@@ -58,7 +76,11 @@ export function RegisterPage() {
       if (!(e instanceof ApiError)) return setError('root', { message: String(e) })
       // Sunucu hatasını ilgili alana bağla
       if (e.code === 'conflict') setError('email', { message: e.message }, { shouldFocus: true })
-      else if (v.mode === 'join' && e.code === 'bad_request' && e.message.includes('Davet'))
+      else if (e.code === 'registration_closed') {
+        // Bu arada başka biri ilk haneyi kurmuş olabilir → bilgiyi tazele, formu davete çevir
+        await qc.invalidateQueries({ queryKey: queryKeys.registration })
+        setError('root', { message: e.message })
+      } else if (v.mode === 'join' && e.code === 'bad_request' && e.message.includes('Davet'))
         setError('invite_code', { message: e.message }, { shouldFocus: true })
       else setError('root', { message: e.message })
     }
@@ -74,7 +96,10 @@ export function RegisterPage() {
       footer={
         <>
           {s.hasAccount}{' '}
-          <Link to={loginLink} className="font-medium text-primary underline-offset-4 hover:underline">
+          <Link
+            to={loginLink}
+            className="font-medium text-primary underline-offset-4 hover:underline"
+          >
             {s.toLogin}
           </Link>
         </>
@@ -105,39 +130,60 @@ export function RegisterPage() {
         {/* Yeni hane mi, davetle katılma mı? */}
         <fieldset className="space-y-3">
           <legend className="mb-2 text-sm font-medium">{s.modeLabel}</legend>
-          <Controller
-            control={control}
-            name="mode"
-            render={({ field }) => (
-              <div role="radiogroup" className="grid grid-cols-2 gap-2 rounded-lg border bg-muted p-1">
-                {(
-                  [
-                    ['new', s.modeNew, Home],
-                    ['join', s.modeJoin, Users],
-                  ] as const
-                ).map(([value, label, Icon]) => (
-                  <button
-                    key={value}
-                    type="button"
-                    role="radio"
-                    aria-checked={field.value === value}
-                    onClick={() => field.onChange(value)}
-                    className={cn(
-                      'flex min-h-11 items-center justify-center gap-2 rounded-md text-sm font-medium text-muted-foreground transition-colors',
-                      field.value === value && 'bg-background text-foreground shadow-sm',
-                    )}
-                  >
-                    <Icon className="size-4" aria-hidden />
-                    {label}
-                  </button>
-                ))}
-              </div>
-            )}
-          />
+          {!newAllowed && (
+            <p className="flex gap-2 rounded-lg bg-muted px-3 py-2.5 text-sm text-muted-foreground">
+              <Info className="mt-0.5 size-4 shrink-0" aria-hidden />
+              {s.closedNote}
+            </p>
+          )}
+          {newAllowed && (
+            <Controller
+              control={control}
+              name="mode"
+              render={({ field }) => (
+                <div
+                  role="radiogroup"
+                  className="grid grid-cols-2 gap-2 rounded-lg border bg-muted p-1"
+                >
+                  {(
+                    [
+                      ['new', s.modeNew, Home],
+                      ['join', s.modeJoin, Users],
+                    ] as const
+                  ).map(([value, label, Icon]) => (
+                    <button
+                      key={value}
+                      type="button"
+                      role="radio"
+                      aria-checked={field.value === value}
+                      onClick={() => field.onChange(value)}
+                      className={cn(
+                        'flex min-h-11 items-center justify-center gap-2 rounded-md text-sm font-medium text-muted-foreground transition-colors',
+                        field.value === value && 'bg-background text-foreground shadow-sm',
+                      )}
+                    >
+                      <Icon className="size-4" aria-hidden />
+                      {label}
+                    </button>
+                  ))}
+                </div>
+              )}
+            />
+          )}
 
           {mode === 'new' ? (
-            <FormField label={s.householdName} error={errors.household_name} hint={s.householdHint(name)}>
-              {(f) => <Input {...f} {...register('household_name')} placeholder={name ? `${name} Hanesi` : ''} />}
+            <FormField
+              label={s.householdName}
+              error={errors.household_name}
+              hint={s.householdHint(name)}
+            >
+              {(f) => (
+                <Input
+                  {...f}
+                  {...register('household_name')}
+                  placeholder={name ? `${name} Hanesi` : ''}
+                />
+              )}
             </FormField>
           ) : (
             <FormField label={s.inviteCode} error={errors.invite_code} hint={s.inviteHint}>