feat(auth): add change password API and frontend page

Backend:
- Add ChangePasswordReq DTO with validation (current + new password)
- Add AuthService::change_password() method with credential verification,
  password rehash, and token revocation
- Add POST /api/v1/auth/change-password endpoint with utoipa annotation

Frontend:
- Add changePassword() API function in auth.ts
- Add ChangePassword.tsx page with form validation and confirmation
- Add "修改密码" tab in Settings page

After password change, all refresh tokens are revoked and the user
is redirected to the login page.

crates/erp-server/src/main.rs

@@ -21,6 +21,7 @@ struct ApiDoc;
         erp_auth::handler::auth_handler::login,
         erp_auth::handler::auth_handler::refresh,
         erp_auth::handler::auth_handler::logout,
+        erp_auth::handler::auth_handler::change_password,
         erp_auth::handler::user_handler::list_users,
         erp_auth::handler::user_handler::create_user,
         erp_auth::handler::user_handler::get_user,
@@ -49,6 +50,7 @@ struct ApiDoc;
             erp_auth::dto::UpdateRoleReq,
             erp_auth::dto::PermissionResp,
             erp_auth::dto::AssignPermissionsReq,
+            erp_auth::dto::ChangePasswordReq,
         )
     )
 )]