fix(console): show OIDC account name for console admin users

[GatewayJ]

Description

This PR fixes the user dropdown showing the hardcoded label rustfsAdmin for OIDC users who have the consoleAdmin policy (and are treated as console administrators). The console previously skipped fetching /accountinfo for admin sessions and substituted a placeholder name.

Changes:

• PermissionsProvider: fetch user policy/account info whenever the user is authenticated and admin resolution is complete, not only for non-admin users.
• UserDropdown: display account_name from the API without the rustfsAdmin fallback (empty string when missing).

This aligns the UI with the API, which returns the OIDC session identity (e.g. preferred_username) for temporary credentials.

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Code refactoring
• Performance improvement
• Test improvements
• Security fix

Testing

• Unit tests added/updated (no test runner configured in this repo)
• Manual testing completed

pnpm install --frozen-lockfile
rm -rf .next && pnpm exec tsc --noEmit
pnpm lint

Note: pnpm test:run is not defined in package.json.

Checklist

• Code follows the project's style guidelines
• Self-review completed
• TypeScript types are properly defined
• All commit messages are in English (Conventional Commits)
• All existing tests pass (no test script in project)
• No new dependencies added, or they are justified

Related Issues

Closes rustfs/rustfs#2612 (console-side; server already returns account_name from OIDC parent_user for temp sessions).

Screenshots (if applicable)

N/A (username text in user menu).

Additional Notes

Upstream issue: rustfs/rustfs#2612