fix(认证): 补齐余额与删除场景缓存失效

为 Usage/Promo/Redeem 注入认证缓存失效逻辑
删除用户与分组前先失效认证缓存降低窗口
补充回归测试验证失效调用

测试: make test

backend/internal/server/api_contract_test.go

@@ -394,7 +394,7 @@ func newContractDeps(t *testing.T) *contractDeps {
 	apiKeyService := service.NewAPIKeyService(apiKeyRepo, userRepo, groupRepo, userSubRepo, apiKeyCache, cfg)
 
 	usageRepo := newStubUsageLogRepo()
-	usageService := service.NewUsageService(usageRepo, userRepo, nil)
+	usageService := service.NewUsageService(usageRepo, userRepo, nil, nil)
 
 	settingRepo := newStubSettingRepo()
 	settingService := service.NewSettingService(settingRepo, cfg)