feat(auth): add comprehensive authentication system with 2FA support

- Add new auth module with captcha, login, logout, register, and email verification endpoints
- Implement two-factor authentication with TOTP enable, disable, verify, and backup codes regeneration
- Create RSA public key endpoint for secure password encryption
- Add user profile management with get current user and email retrieval
- Integrate OpenAPI documentation for all authentication endpoints
- Implement password reset functionality with email verification flow
- Add comprehensive API response structures with proper error handling
- Configure all auth routes under /api/v1/auth scope with proper tagging

api/auth/enable_2fa.rs

@@ -0,0 +1,29 @@
+use actix_web::{HttpResponse, web};
+
+use crate::api::response::{ApiErrorResponse, ApiResponse};
+use crate::error::AppError;
+use crate::service::AppService;
+use crate::service::auth::totp::Enable2FAResponse;
+use crate::session::Session;
+
+#[utoipa::path(
+    post,
+    path = "/api/v1/auth/2fa/enable",
+    tag = "Auth / 2FA",
+    operation_id = "authPrepareTwoFactorEnable",
+    summary = "Initialize two-factor authentication setup",
+    description = "Generate a new TOTP secret, otpauth QR-code URI, and 10 one-time backup codes for the current signed-in user, and save them in a not-yet-enabled state. Clients must guide the user to scan the QR code and call /auth/2fa/verify with a dynamic code before 2FA is actually enabled. Backup codes are returned in plaintext only once in this response; frontends must remind users to store them securely.",
+    responses(
+        (status = 200, description = "2FA setup initialized successfully. Returns the secret, QR-code URI, and backup codes.", body = ApiResponse<Enable2FAResponse>),
+        (status = 400, description = "The current user has already enabled 2FA.", body = ApiErrorResponse),
+        (status = 401, description = "The current session is not authenticated.", body = ApiErrorResponse),
+        (status = 500, description = "Database write or backup code hashing failed.", body = ApiErrorResponse)
+    )
+)]
+pub async fn handle(
+    service: web::Data<AppService>,
+    session: Session,
+) -> Result<HttpResponse, AppError> {
+    let data = service.auth.auth_2fa_enable(&session).await?;
+    Ok(HttpResponse::Ok().json(ApiResponse::new(data)))
+}