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/monitoring/health.go

@@ -14,10 +14,10 @@ import (
 type HealthStatus string
 
 const (
-	HealthStatusUP      HealthStatus = "UP"
-	HealthStatusDOWN    HealthStatus = "DOWN"
+	HealthStatusUP       HealthStatus = "UP"
+	HealthStatusDOWN     HealthStatus = "DOWN"
 	HealthStatusDEGRADED HealthStatus = "DEGRADED"
-	HealthStatusUNKNOWN HealthStatus = "UNKNOWN"
+	HealthStatusUNKNOWN  HealthStatus = "UNKNOWN"
 )
 
 // HealthCheck 健康检查器（增强版，支持 Redis 检查）

internal/monitoring/metrics.go

@@ -126,15 +126,15 @@ func GetGlobalMetrics() *Metrics {
 	globalMetricsOnce.Do(func() {
 		m := NewMetrics()
 		// 将私有 registry 的指标也注册到默认 registry
-		prometheus.DefaultRegisterer.Register(m.httpRequestsTotal)        //nolint:errcheck
-		prometheus.DefaultRegisterer.Register(m.httpRequestDuration)      //nolint:errcheck
-		prometheus.DefaultRegisterer.Register(m.dbQueriesTotal)           //nolint:errcheck
-		prometheus.DefaultRegisterer.Register(m.dbQueryDuration)          //nolint:errcheck
-		prometheus.DefaultRegisterer.Register(m.userRegistrations)        //nolint:errcheck
-		prometheus.DefaultRegisterer.Register(m.userLogins)               //nolint:errcheck
-		prometheus.DefaultRegisterer.Register(m.activeUsers)              //nolint:errcheck
-		prometheus.DefaultRegisterer.Register(m.systemMemoryUsage)        //nolint:errcheck
-		prometheus.DefaultRegisterer.Register(m.systemGoroutines)         //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.httpRequestsTotal)   //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.httpRequestDuration) //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.dbQueriesTotal)      //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.dbQueryDuration)     //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.userRegistrations)   //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.userLogins)          //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.activeUsers)         //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.systemMemoryUsage)   //nolint:errcheck
+		prometheus.DefaultRegisterer.Register(m.systemGoroutines)    //nolint:errcheck
 		globalMetrics = m
 	})
 	return globalMetrics

internal/monitoring/slo.go

@@ -10,7 +10,7 @@ import (
 // 这些指标是 SLO 测量的基础，用于计算错误预算燃烧率
 type SLOMetrics struct {
 	// 缓存命中统计（alerts.yml 引用但原来未定义）
-	CacheHitsTotal      *prometheus.CounterVec
+	CacheHitsTotal       *prometheus.CounterVec
 	CacheOperationsTotal *prometheus.CounterVec
 
 	// 数据库连接池状态（alerts.yml 引用但原来未定义）
@@ -21,8 +21,8 @@ type SLOMetrics struct {
 	TokenRefreshTotal *prometheus.CounterVec
 
 	// 账号安全事件
-	AccountLockTotal      prometheus.Counter
-	AnomalyDetectedTotal  *prometheus.CounterVec
+	AccountLockTotal     prometheus.Counter
+	AnomalyDetectedTotal *prometheus.CounterVec
 
 	// 错误预算燃烧率（可选，用于自定义仪表盘）
 	ErrorBudgetBurnRate *prometheus.GaugeVec