test: add comprehensive test coverage and improve code quality

- Add new test files for auth, service, and handler modules
- Improve test organization and coverage
- Refactor code for better maintainability
- Add captcha, settings, stats, and theme handler tests
- Add auth module tests (CAS, OAuth, password, SSO, state)
- Add service layer tests for auth, export, permissions, roles
- All Go tests pass (exit code 0)
- All frontend tests pass (325 tests in 59 files)

internal/integration/integration_test.go

@@ -9,10 +9,10 @@ import (
 	"sync/atomic"
 	"testing"
 
-	_ "modernc.org/sqlite" // 纯 Go SQLite，注册 "sqlite" 驱动
 	gormsqlite "gorm.io/driver/sqlite"
 	"gorm.io/gorm"
 	"gorm.io/gorm/logger"
+	_ "modernc.org/sqlite" // 纯 Go SQLite，注册 "sqlite" 驱动
 
 	"github.com/user-management-system/internal/domain"
 	"github.com/user-management-system/internal/repository"
@@ -138,12 +138,12 @@ func TestTransactionIntegration(t *testing.T) {
 
 	t.Run("TransactionRollback", func(t *testing.T) {
 		err := db.Transaction(func(tx *gorm.DB) error {
-		user := &domain.User{
-			Phone:    domain.StrPtr("13811111111"),
-			Username: "txrollbackuser",
-			Password: "hashedpassword",
-			Status:   domain.UserStatusActive,
-		}
+			user := &domain.User{
+				Phone:    domain.StrPtr("13811111111"),
+				Username: "txrollbackuser",
+				Password: "hashedpassword",
+				Status:   domain.UserStatusActive,
+			}
 			if err := tx.Create(user).Error; err != nil {
 				return err
 			}
@@ -162,12 +162,12 @@ func TestTransactionIntegration(t *testing.T) {
 
 	t.Run("TransactionCommit", func(t *testing.T) {
 		err := db.Transaction(func(tx *gorm.DB) error {
-		user := &domain.User{
-			Phone:    domain.StrPtr("13822222222"),
-			Username: "txcommituser",
-			Password: "hashedpassword",
-			Status:   domain.UserStatusActive,
-		}
+			user := &domain.User{
+				Phone:    domain.StrPtr("13822222222"),
+				Username: "txcommituser",
+				Password: "hashedpassword",
+				Status:   domain.UserStatusActive,
+			}
 			return tx.Create(user).Error
 		})
 		if err != nil {