Feat/add admin check

[KMerdan]

Summary

This PR introduces a new is_admin property in the Account model and the corresponding utility method is_admin_role in the TenantAccountRole class. These changes enhance access control and ensure only administrators can manage critical application settings if required.

Key Changes:

• Added is_admin property to the Account model to simplify admin checks.

• Added is_admin_role static method to TenantAccountRole to encapsulate role-specific logic.

Screenshots

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Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods