fix: improve RouteCache tenant route loading logic

- Change from if-else if to separate if statements
- Ensure tenant routes are loaded regardless of IsGlobal flag
- Add detailed logging for route loading
- Fix null check for GetRoute parameters

src/yarpgateway/Services/RouteCache.cs

@@ -129,16 +129,29 @@ public class RouteCache : IRouteCache
                     IsGlobal = route.IsGlobal
                 };
 
+                // 1. 全局路由
                 if (route.IsGlobal)
                 {
                     _globalRoutes[route.ServiceName] = routeInfo;
                     _pathRoutes[pathPattern] = routeInfo;
+                    _logger.LogDebug("Loaded global route: {Service} -> {Cluster}", 
+                        route.ServiceName, route.ClusterId);
                 }
-                else if (!string.IsNullOrEmpty(route.TenantCode))
+                
+                // 2. 租户专属路由（无论 IsGlobal 值如何，只要有 TenantCode 就添加到租户路由表）
+                if (!string.IsNullOrEmpty(route.TenantCode))
                 {
-                    _tenantRoutes.GetOrAdd(route.TenantCode, _ => new())
+                    _tenantRoutes.GetOrAdd(route.TenantCode, _ => new ConcurrentDictionary<string, RouteInfo>())
                         [route.ServiceName] = routeInfo;
-                    _pathRoutes[pathPattern] = routeInfo;
+                    
+                    // 如果不是全局路由，也添加到路径路由
+                    if (!route.IsGlobal)
+                    {
+                        _pathRoutes[pathPattern] = routeInfo;
+                    }
+                    
+                    _logger.LogDebug("Loaded tenant route: {Tenant}/{Service} -> {Cluster}", 
+                        route.TenantCode, route.ServiceName, route.ClusterId);
                 }
             }
         }