Plan:
1.  **Move Menu Item:** Moved "Register Sessions" from the "Administration" section to the "Reports" section in the sidebar.
2.  **Update Permissions:** Updated the internal `$permission_groups` array to reflect this structural change.

Changed:
*   `index.php`: Moved the `register_sessions` permission and the corresponding sidebar link and logic.

Notes:
*   "Register Sessions" is now located under the "Reports" dropdown in the sidebar.
*   It remains accessible to users who could access it before (logic uses the same permission keys), but is now grouped with reports.

Next: Verify that "Register Sessions" appears in the Reports section and functions correctly.