Callers that build an encrypted store had to depend on `libchat` directly for
`ChatStorage`, and `ChatClientBuilder::storage_config` panicked on a bad config,
which aborts the process under `panic = "abort"`.
- Re-export `ChatStorage` from logos-chat so callers can name the store type
without a direct `libchat` dependency.
- `storage_config` now returns `Result<_, ChatError>` instead of `.expect()`, so
an unopenable database surfaces as an error. Updates the chat-cli callers.
