feat(web): improve login error layout and add Terms of Service link

- Improve backend connection error display with bordered container,
  inline icon, and better visual hierarchy
- Extract actual error message from axios response object
- Add Terms of Service link (https://langbot.app/terms) to login footer
- Add termsOfService i18n key for all 7 locales

web/src/i18n/locales/en-US.ts

@@ -63,6 +63,7 @@ const enUS = {
     test: 'Test',
     forgotPassword: 'Forgot Password?',
     agreementNotice: 'By continuing, you agree to our',
+    termsOfService: 'Terms of Service',
     privacyPolicy: 'Privacy Policy',
     and: 'and',
     dataCollectionPolicy: 'Data Collection Policy',

web/src/i18n/locales/es-ES.ts

@@ -64,7 +64,8 @@ const esES = {
     copyFailed: 'Error al copiar',
     test: 'Probar',
     forgotPassword: '¿Olvidaste tu contraseña?',
-    agreementNotice: 'Al continuar, aceptas nuestra',
+    agreementNotice: 'Al continuar, aceptas nuestros',
+    termsOfService: 'Términos de servicio',
     privacyPolicy: 'Política de privacidad',
     and: 'y',
     dataCollectionPolicy: 'Política de recopilación de datos',

web/src/i18n/locales/ja-JP.ts

@@ -64,6 +64,7 @@ const jaJP = {
     test: 'テスト',
     forgotPassword: 'パスワードを忘れた？',
     agreementNotice: '続行することで、以下に同意したものとみなされます：',
+    termsOfService: '利用規約',
     privacyPolicy: 'プライバシーポリシー',
     and: 'および',
     dataCollectionPolicy: 'データ収集ポリシー',

web/src/i18n/locales/th-TH.ts

@@ -63,6 +63,7 @@ const thTH = {
     test: 'ทดสอบ',
     forgotPassword: 'ลืมรหัสผ่าน?',
     agreementNotice: 'การดำเนินการต่อแสดงว่าคุณยอมรับ',
+    termsOfService: 'ข้อกำหนดการให้บริการ',
     privacyPolicy: 'นโยบายความเป็นส่วนตัว',
     and: 'และ',
     dataCollectionPolicy: 'นโยบายการเก็บรวบรวมข้อมูล',

web/src/i18n/locales/vi-VN.ts

@@ -63,6 +63,7 @@ const viVN = {
     test: 'Kiểm tra',
     forgotPassword: 'Quên mật khẩu?',
     agreementNotice: 'Bằng việc tiếp tục, bạn đồng ý với',
+    termsOfService: 'Điều khoản dịch vụ',
     privacyPolicy: 'Chính sách bảo mật',
     and: 'và',
     dataCollectionPolicy: 'Chính sách thu thập dữ liệu',

web/src/i18n/locales/zh-Hans.ts

@@ -62,6 +62,7 @@ const zhHans = {
     test: '测试',
     forgotPassword: '忘记密码？',
     agreementNotice: '继续即表示您同意我们的',
+    termsOfService: '服务条款',
     privacyPolicy: '隐私政策',
     and: '和',
     dataCollectionPolicy: '数据收集政策',

web/src/i18n/locales/zh-Hant.ts

@@ -62,6 +62,7 @@ const zhHant = {
     test: '測試',
     forgotPassword: '忘記密碼？',
     agreementNotice: '繼續即表示您同意我們的',
+    termsOfService: '服務條款',
     privacyPolicy: '隱私政策',
     and: '和',
     dataCollectionPolicy: '數據收集政策',