feat(api): implement user authentication and registration endpoints

- Add main application logic in `api/src/main.rs` to initialize server, database, and services.
- Create authentication routes in `api/src/routes/auth.rs` for login, register, logout, and user info retrieval.
- Implement configuration route in `api/src/routes/config.rs` to expose application settings.
- Define application state management in `api/src/state.rs` to share user service and configuration.
- Set up Docker Compose configuration in `compose.yml` for backend, worker, and database services.
- Establish domain logic in `domain` crate with user entities, repositories, and services.
- Implement SQLite user repository in `infra/src/user_repository.rs` for user data persistence.
- Create database migration handling in `infra/src/db.rs` and session store in `infra/src/session_store.rs`.
- Add necessary dependencies and features in `Cargo.toml` files for both `domain` and `infra` crates.

domain/src/lib.rs

@@ -0,0 +1,17 @@
+//! Domain Logic
+//!
+//! This crate contains the core business logic, entities, and repository interfaces.
+//! It is completely independent of the infrastructure layer (databases, HTTP, etc.).
+
+pub mod entities;
+pub mod errors;
+pub mod repositories;
+pub mod services;
+pub mod value_objects;
+
+// Re-export commonly used types
+pub use entities::*;
+pub use errors::{DomainError, DomainResult};
+pub use repositories::*;
+pub use services::UserService;
+pub use value_objects::*;