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/locales/zh.json

@@ -71,7 +71,17 @@
       "providerCustomOption": "🔧 Custom OpenAI-Compatible",
       "saved": "(已保存)",
       "chatProvider": "聊天提供商",
-      "chatDescription": "用于聊天助手的 AI 提供商。如果未配置，将回退到标签提供商。"
+      "chatDescription": "用于聊天助手的 AI 提供商。如果未配置，将回退到标签提供商。",
+      "fetchModelsFailed": "获取模型失败",
+      "refreshModels": "刷新模型",
+      "configured": "已配置",
+      "fetchingModels": "正在获取模型...",
+      "clickToLoadModels": "点击 ↺ 加载模型",
+      "searchModel": "搜索模型...",
+      "noModels": "无模型。点击 ↺",
+      "modelsAvailable": "{count} 个模型可用",
+      "enterUrlToLoad": "输入URL并点击↺加载模型",
+      "currentProvider": "(当前: {provider})"
     },
     "aiTest": {
       "description": "测试您的 AI 提供商的标签生成和语义搜索嵌入",
@@ -217,8 +227,11 @@
       "jinaKeyDescription": "用于网页抓取。无密钥也可使用，但有速率限制。",
       "saveSettings": "保存工具设置",
       "updateSuccess": "工具设置更新成功",
-      "updateFailed": "更新工具设置失败"
-    }
+      "updateFailed": "更新工具设置失败",
+      "testing": "测试中...",
+      "testSearch": "测试网络搜索"
+    },
+    "settingsDescription": "配置应用程序设置"
   },
   "ai": {
     "analyzing": "AI 分析中...",
@@ -368,7 +381,9 @@
     "signIn": "登录",
     "signInToAccount": "登录您的账户",
     "signOut": "退出登录",
-    "signUp": "注册"
+    "signUp": "注册",
+    "confirmPassword": "确认密码",
+    "confirmPasswordPlaceholder": "再次输入密码"
   },
   "autoLabels": {
     "analyzing": "分析您的笔记...",