Refactor error handling in IAM and CMS crates

- Introduced `RepositoryError` and `ServiceError` enums in both IAM and CMS domains for better error management.
- Updated domain traits and services to return specific error types instead of `anyhow::Result`.
- Enhanced session and OAuth repository implementations to handle errors more explicitly.
- Refactored session service methods to return `Result<T, ServiceError>` for improved error handling.
- Updated HTTP handlers to utilize the new error types.
- Modified password hashing functions to run in a blocking context using `tokio::task::spawn_blocking`.
- Added tests for new error handling mechanisms and async password functions.

crates/zesdex-iam/src/domain/mod.rs

@@ -11,6 +11,7 @@
 //! - [`service`] — Trait definitions: `OAuthService`, `SessionService`
 //! - [`session`] — `Session` entity (IAM wrapper around `zesdex_entities::Session`)
 
+pub mod error;
 pub mod oauth;
 pub mod repository;
 pub mod service;