Kaapi v1.0: Permissions Review

[AkhileshNegi]

Is your feature request related to a problem?
Our permissions setup needs a cleanup pass. After recent auth changes, we need to:

• Review all FastAPI routes and ensure permissions are enforced consistently.
• Remove any old authorization logic or unused dependencies related to the previous system.
• Confirm that all Depends() and Security() usages are relevant and actively used.