feat(auth): implement JWT authentication and user registration

- Added JWT authentication with token generation and validation.
- Introduced user registration functionality with email and password.
- Integrated Argon2 for password hashing.
- Created SQLite user repository for user data persistence.
- Updated application context to include user repository and configuration settings.
- Added environment variable support for JWT secret and registration allowance.
- Enhanced error handling for unauthorized access and validation errors.
- Updated presentation layer to handle login and registration requests.

crates/application/src/use_cases/register.rs

@@ -0,0 +1,18 @@
+use domain::{errors::DomainError, models::User, value_objects::Email};
+
+use crate::{commands::RegisterCommand, context::AppContext};
+
+pub async fn execute(ctx: &AppContext, cmd: RegisterCommand) -> Result<(), DomainError> {
+    if !ctx.config.allow_registration {
+        return Err(DomainError::Unauthorized("Registration is disabled".into()));
+    }
+
+    let email = Email::new(cmd.email)?;
+
+    if ctx.user_repository.find_by_email(&email).await?.is_some() {
+        return Err(DomainError::ValidationError("Email already registered".into()));
+    }
+
+    let hash = ctx.password_hasher.hash(&cmd.password).await?;
+    ctx.user_repository.save(&User::new(email, hash)).await
+}