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/register_email_code.rs

@@ -0,0 +1,38 @@
+use actix_web::{HttpResponse, web};
+
+use crate::api::response::{ApiErrorResponse, ApiResponse};
+use crate::error::AppError;
+use crate::service::AppService;
+use crate::service::auth::register::{RegisterEmailCodeParams, RegisterEmailCodeResponse};
+use crate::session::Session;
+
+#[utoipa::path(
+    post,
+    path = "/api/v1/auth/register/email-code",
+    tag = "Auth",
+    operation_id = "authSendRegisterEmailCode",
+    summary = "Send registration email verification code",
+    description = "After validating the captcha in the current session, send a 6-digit registration code to the target email address. The endpoint checks whether a verified email already exists and applies a per-email cooldown to prevent email bombing. The code is valid for 10 minutes by default.",
+    request_body(
+        content = RegisterEmailCodeParams,
+        description = "The target email address and captcha from the current session.",
+        content_type = "application/json"
+    ),
+    responses(
+        (status = 200, description = "The verification email has been queued for delivery. Returns the code expiration time.", body = ApiResponse<RegisterEmailCodeResponse>),
+        (status = 400, description = "The captcha is incorrect, the email is empty, or requests are too frequent.", body = ApiErrorResponse),
+        (status = 409, description = "The email is already used by another verified account.", body = ApiErrorResponse),
+        (status = 500, description = "Cache write failed or the email service is unavailable.", body = ApiErrorResponse)
+    )
+)]
+pub async fn handle(
+    service: web::Data<AppService>,
+    session: Session,
+    params: web::Json<RegisterEmailCodeParams>,
+) -> Result<HttpResponse, AppError> {
+    let data = service
+        .auth
+        .auth_register_email_code(params.into_inner(), &session)
+        .await?;
+    Ok(HttpResponse::Ok().json(ApiResponse::new(data)))
+}