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/api/handler/export_handler.go

@@ -107,8 +107,8 @@ func (h *ExportHandler) ImportUsers(c *gin.Context) {
 		"code": 0,
 		"data": gin.H{
 			"success_count": successCount,
-			"fail_count":   failCount,
-			"errors":       errs,
+			"fail_count":    failCount,
+			"errors":        errs,
 		},
 	})
 }