Refactor session ID handling and improve error management

- Introduced `SessionId` newtype for validated session identifiers, ensuring safety against path traversal attacks.
- Updated session repository methods to accept `SessionId` instead of raw strings, enhancing type safety.
- Removed redundant error handling in repository methods by leveraging the new `Error` type from `zesdex_utils`.
- Simplified atomic JSON write operations by eliminating unnecessary error conversions.
- Enhanced integer casting with a new `CastOr` trait for safer narrowing conversions.
- Removed deprecated error handling code and consolidated error types across the codebase.
- Updated HTTP handlers to utilize the new session ID validation, improving overall robustness.

crates/zesdex-cms/src/infrastructure/persistence/app_config_repo.rs

@@ -156,8 +156,7 @@ impl AppConfigRepository for JsonAppConfigRepository {
         tracing::debug!("saving app_config to {base_dir:?}");
         std::fs::create_dir_all(base_dir)?;
         let path = base_dir.join("app_config.json");
-        write_json_atomic(&path, config, None)
-            .map_err(RepositoryError::from_anyhow)?;
+        write_json_atomic(&path, config, None)?;
         tracing::debug!("app_config saved to '{}'", path.display());
         Ok(())
     }