Add descriptions and KV contentType properties to secret rotation configurations

For better self-documentation, the configs should include descriptions and key vault secrets should have a useful ContentType

No files, tests, or entry points are named in the issue. Start by locating the secret rotation configuration definitions and the Key Vault secret creation path, then identify the expected description and ContentType values. Done means configurations expose descriptions and rotated Key Vault secrets have useful ContentType values.

Written by the indexing model from the issue text.