Remove next-intl localization infrastructure

Strips out the i18n layer (next-intl, message files, language switcher,
provider) to reduce complexity. Nav components now use plain English strings.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/components/layouts/admin-sidebar.tsx

@@ -5,7 +5,6 @@ import Link from 'next/link'
 import type { Route } from 'next'
 import { usePathname } from 'next/navigation'
 import { signOut } from 'next-auth/react'
-import { useTranslations } from 'next-intl'
 import { cn } from '@/lib/utils'
 import { Button } from '@/components/ui/button'
 import {
@@ -42,7 +41,6 @@ import { EditionSelector } from '@/components/shared/edition-selector'
 import { useEdition } from '@/contexts/edition-context'
 import { UserAvatar } from '@/components/shared/user-avatar'
 import { NotificationBell } from '@/components/shared/notification-bell'
-import { LanguageSwitcher } from '@/components/shared/language-switcher'
 import { useSession } from 'next-auth/react'
 import { trpc } from '@/lib/trpc/client'
 
@@ -147,7 +145,6 @@ const roleLabels: Record<string, string> = {
 
 export function AdminSidebar({ user }: AdminSidebarProps) {
   const pathname = usePathname()
-  const tAuth = useTranslations('auth')
   const [isMobileMenuOpen, setIsMobileMenuOpen] = useState(false)
   const { status: sessionStatus } = useSession()
   const isAuthenticated = sessionStatus === 'authenticated'
@@ -173,7 +170,6 @@ export function AdminSidebar({ user }: AdminSidebarProps) {
       <div className="fixed top-0 left-0 right-0 z-40 flex h-16 items-center justify-between border-b bg-card px-4 lg:hidden">
         <Logo showText textSuffix="Admin" />
         <div className="flex items-center gap-2">
-          <LanguageSwitcher />
           <NotificationBell />
           <Button
             variant="ghost"
@@ -209,7 +205,6 @@ export function AdminSidebar({ user }: AdminSidebarProps) {
         <div className="flex h-16 items-center justify-between border-b px-6">
           <Logo showText textSuffix="Admin" />
           <div className="hidden lg:flex items-center gap-1">
-            <LanguageSwitcher />
             <NotificationBell />
           </div>
         </div>
@@ -349,7 +344,7 @@ export function AdminSidebar({ user }: AdminSidebarProps) {
                 className="flex cursor-pointer items-center gap-2.5 rounded-md px-2 py-2 text-destructive focus:bg-destructive/10 focus:text-destructive"
               >
                 <LogOut className="h-4 w-4" />
-                <span>{tAuth('signOut')}</span>
+                <span>Sign Out</span>
               </DropdownMenuItem>
             </DropdownMenuContent>
           </DropdownMenu>