feat: Control the allowed login methods via Super Admin (#12892)

- Control the allowed authentication methods for a chatwoot installation
via super admin configs. [SAML, Google Auth etc]
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[Codex
Task](https://chatgpt.com/codex/tasks/task_e_6917d503b6e48326a261672c1de91462)

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Co-authored-by: Pranav <pranav@chatwoot.com>
Co-authored-by: Sivin Varghese <64252451+iamsivin@users.noreply.github.com>

config/locales/en.yml

@@ -64,6 +64,7 @@ en:
       not_found: Assignment policy not found
     saml:
       feature_not_enabled: SAML feature not enabled for this account
+      sso_not_enabled: SAML SSO is not enabled for this installation
     data_import:
       data_type:
         invalid: Invalid data type