Improve role and permission controls across dashboard and controller

[simplecloud-vercel-github]

Problem

Role and permission handling needs more precise, predictable controls across the dashboard and controller.

Expected behavior

Administrators should be able to configure permissions consistently in both interfaces, with access limited to the appropriate server and resource.

Requested improvements

• Provide finer-grained role and permission controls.
• Support per-server permission scoping.
• Allow permissions to govern plugin and file access.
• Distinguish upload, edit, and delete permissions for files.
• Make permission behavior clear and consistent between the dashboard and controller.

Acceptance criteria

• Roles can be assigned only the capabilities intended for them.
• Server-scoped permissions do not grant access to other servers.
• Plugin and file access can be controlled independently where applicable.
• Upload, edit, and delete file operations can be granted or denied separately.
• Equivalent permission settings have consistent, understandable results in the dashboard and controller.