fix(P2): 修复4个P2轻微问题

P2-01: 通配符scope安全风险 (scope_auth.go)
- 添加hasWildcardScope()函数检测通配符scope
- 添加logWildcardScopeAccess()函数记录审计日志
- 在RequireScope/RequireAllScopes/RequireAnyScope中间件中调用审计日志

P2-02: isSamePayload比较字段不完整 (audit_service.go)
- 添加ActionDetail字段比较
- 添加ResultMessage字段比较
- 添加Extensions字段比较
- 添加compareExtensions()辅助函数

P2-03: regexp.MustCompile可能panic (sanitizer.go)
- 添加compileRegex()安全编译函数替代MustCompile
- 处理编译错误，避免panic

P2-04: StrategyRoundRobin未实现 (router.go)
- 添加selectByRoundRobin()方法
- 添加roundRobinCounter原子计数器
- 使用atomic.AddUint64实现线程安全的轮询

P2-05: 错误信息泄露内部细节 - 已在MED-09中处理，跳过

gateway/internal/router/router.go

@@ -5,6 +5,7 @@ import (
 	"math"
 	"math/rand"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"lijiaoqiao/gateway/internal/adapter"
@@ -36,10 +37,11 @@ type ProviderHealth struct {
 
 // Router 路由器
 type Router struct {
-	providers map[string]adapter.ProviderAdapter
-	health    map[string]*ProviderHealth
-	strategy  LoadBalancerStrategy
-	mu        sync.RWMutex
+	providers         map[string]adapter.ProviderAdapter
+	health            map[string]*ProviderHealth
+	strategy          LoadBalancerStrategy
+	mu                sync.RWMutex
+	roundRobinCounter uint64 // RoundRobin策略的原子计数器
 }
 
 // NewRouter 创建路由器
@@ -87,6 +89,8 @@ func (r *Router) SelectProvider(ctx context.Context, model string) (adapter.Prov
 	switch r.strategy {
 	case StrategyLatency:
 		return r.selectByLatency(candidates)
+	case StrategyRoundRobin:
+		return r.selectByRoundRobin(candidates)
 	case StrategyWeighted:
 		return r.selectByWeight(candidates)
 	case StrategyAvailability:
@@ -121,6 +125,16 @@ func (r *Router) isProviderAvailable(name, model string) bool {
 	return false
 }
 
+func (r *Router) selectByRoundRobin(candidates []string) (adapter.ProviderAdapter, error) {
+	if len(candidates) == 0 {
+		return nil, gwerror.NewGatewayError(gwerror.ROUTER_NO_PROVIDER_AVAILABLE, "no available provider")
+	}
+
+	// 使用原子操作进行轮询选择
+	index := atomic.AddUint64(&r.roundRobinCounter, 1) - 1
+	return r.providers[candidates[index%uint64(len(candidates))]], nil
+}
+
 func (r *Router) selectByLatency(candidates []string) (adapter.ProviderAdapter, error) {
 	var bestProvider adapter.ProviderAdapter
 	var minLatency int64 = math.MaxInt64