feat(api-key): 添加 IP 白名单/黑名单限制功能 (#221)

* feat(api-key): add IP whitelist/blacklist restriction and usage log IP tracking

- Add IP restriction feature for API keys (whitelist/blacklist with CIDR support)
- Add IP address logging to usage logs (admin-only visibility)
- Remove billing_type column from usage logs UI (redundant)
- Use generic "Access denied" error message for security

Backend:
- New ip package with IP/CIDR validation and matching utilities
- Database migrations for ip_whitelist, ip_blacklist (api_keys) and ip_address (usage_logs)
- Middleware IP restriction check after API key validation
- Input validation for IP/CIDR patterns on create/update

Frontend:
- API key form with enable toggle for IP restriction
- Shield icon indicator in table for keys with IP restriction
- Removed billing_type filter and column from usage views

* fix: update API contract tests for ip_whitelist/ip_blacklist fields

Add ip_whitelist and ip_blacklist fields to expected JSON responses
in API contract tests to match the new API key schema.

backend/internal/service/gateway_service.go

@@ -2247,6 +2247,7 @@ type RecordUsageInput struct {
 	Account      *Account
 	Subscription *UserSubscription // 可选：订阅信息
 	UserAgent    string            // 请求的 User-Agent
+	IPAddress    string            // 请求的客户端 IP 地址
 }
 
 // RecordUsage 记录使用量并扣费（或更新订阅用量）
@@ -2337,6 +2338,11 @@ func (s *GatewayService) RecordUsage(ctx context.Context, input *RecordUsageInpu
 		usageLog.UserAgent = &input.UserAgent
 	}
 
+	// 添加 IPAddress
+	if input.IPAddress != "" {
+		usageLog.IPAddress = &input.IPAddress
+	}
+
 	// 添加分组和订阅关联
 	if apiKey.GroupID != nil {
 		usageLog.GroupID = apiKey.GroupID