Add rate limiting for encryption

**Problem**
When working with handlers, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

Start by locating the handlers and encryption entry points in the Shell project, then determine how requests are currently processed and where errors are reported. Clarify the rate-limit policy, encryption operations it covers, and the required error details with maintainers. Done means rate limiting and descriptive errors are implemented and verified for the relevant handler flows.

Written by the indexing model from the issue text.