Add Dev Tool for Device Secret Override

Summary

Previously, guests were always treated as new users. With the roomserver implementation, the device secret is now reused across tabs/windows. This makes it harder to test multi-user scenarios locally. The new flag enables testers to generate a new device identity upon joining without manually clearing localStorage

After calling the function the choice is persisted across tabs by storing it in the localStorage

Technical Implementation

• call setForceNewDeviceSecret() with either 1 or true to enable the feature
• call setForceNewDeviceSecret() with either 0 or false to disable the feature

Acceptance Criteria

• setForceNewDeviceSecret() is callable from within the browser console