feat: refine i18n for login method selection button (#6771)

#### What type of PR is this?

/area core
/kind improvement
/milestone 2.20.x

#### What this PR does / why we need it:

完善登录方式选择按钮的 i18n。

#### Which issue(s) this PR fixes:

Fixes https://github.com/halo-dev/halo/issues/6759

#### Does this PR introduce a user-facing change?

```release-note
None
```

application/src/main/resources/templates/gateway_modules/login_fragments.html

@@ -10,7 +10,9 @@
             <li th:each="provider : ${formAuthProviders}">
                 <a th:href="'/login?method=' + ${provider.metadata.name}">
                     <img th:src="${provider.spec.logo}" />
-                    <span th:text="${provider.spec.displayName}"></span>
+                    <span
+                        th:text="${#messages.msgOrNull('formAuthProviders.' + provider.metadata.name + '.displayName') ?: provider.spec.displayName}"
+                    ></span>
                 </a>
             </li>
         </ul>

application/src/main/resources/templates/gateway_modules/login_fragments.properties

@@ -1,4 +1,7 @@
 otherLogin.label=其他登录方式
 signup.description=没有账号？
 signup.link=立即注册
-returnToSite=返回网站
+returnToSite=返回网站
+
+# Rule: `formAuthProviders.${provider.metadata.name}.displayName`
+formAuthProviders.local.displayName=账号密码登录

application/src/main/resources/templates/gateway_modules/login_fragments_en.properties

@@ -1,4 +1,7 @@
 otherLogin.label=Other Login
 signup.description=Don't have an account?
 signup.link=Sign up
-returnToSite=Return to site
+returnToSite=Return to site
+
+# Rule: `formAuthProviders.${provider.metadata.name}.displayName`
+formAuthProviders.local.displayName=Login with credentials

application/src/main/resources/templates/gateway_modules/login_fragments_es.properties

@@ -1,4 +1,7 @@
 otherLogin.label=Otras formas de inicio de sesión
 signup.description=¿No tienes una cuenta?
 signup.link=Regístrate ahora
-returnToSite=Volver al sitio
+returnToSite=Volver al sitio
+
+# Rule: `formAuthProviders.${provider.metadata.name}.displayName`
+formAuthProviders.local.displayName=Iniciar sesión con credenciales

application/src/main/resources/templates/gateway_modules/login_fragments_zh_TW.properties

@@ -1,5 +1,7 @@
-
 otherLogin.label=其他登入方式
 signup.description=沒有帳號？
 signup.link=立即註冊
-returnToSite=返回網站
+returnToSite=返回網站
+
+# Rule: `formAuthProviders.${provider.metadata.name}.displayName`
+formAuthProviders.local.displayName=帳號密碼登入