feat: add password confirmation to register + fix i18n hardcoded strings

- Add confirmPassword field to registration form with Zod validation
- Replace ~30 hardcoded French/English strings in admin-settings-form
  with proper t() i18n calls (Ollama models, Custom models, search test)
- Extract SettingsHeader to client component for i18n support
- Add 15 i18n keys to all 15 locale files (auth + admin.ai + admin.tools)
- Remove debug "Config value" line from embeddings section

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

memento-note/app/(admin)/admin/settings/page.tsx

@@ -1,20 +1,13 @@
 import { getSystemConfig } from '@/app/actions/admin-settings'
 import { AdminSettingsForm } from './admin-settings-form'
+import { SettingsHeader } from './settings-header'
 
 export default async function AdminSettingsPage() {
   const config = await getSystemConfig()
 
   return (
     <div className="space-y-6">
-      <div>
-        <h1 className="text-3xl font-bold text-gray-900 dark:text-white">
-          Settings
-        </h1>
-        <p className="text-gray-600 dark:text-gray-400 mt-1">
-          Configure application-wide settings
-        </p>
-      </div>
-
+      <SettingsHeader />
       <div className="bg-white dark:bg-zinc-900 rounded-lg shadow overflow-hidden border border-gray-200 dark:border-gray-800 p-6">
         <AdminSettingsForm config={config} />
       </div>