Remove org selection feature

[craigyu]

Description

The app currently forces users to select an org on login and also exposes org selection in the profile side menu. Remove both entry points.

Silva should infer user privileges automatically instead of requiring manual org selection. As part of this refactor, preserve user privilege data in user context so it can be reused later by a user permissions page.

Scope

• Remove forced org selection during login.
• Remove org selection from the profile side menu.
• Keep user privilege data available in user context.

Acceptance Criteria

• Users can log in without selecting an org.
• Profile side menu no longer shows org selection UI.
• User context still includes privilege data after login/session load.