feat: allow changing tunnel when editing forward rules

- Add tunnelId field to ForwardUpdateDto
- Refactor updateForward to support tunnel change:
  - Release old tunnel resources (GOST services + ForwardPort)
  - Allocate new tunnel resources with proper rollback
  - Preserve flow statistics (inFlow/outFlow)
- Remove tunnel selector disabled state in forward.tsx
- Bump version to 2.0.9

springboot-backend/src/main/java/com/admin/common/dto/ForwardUpdateDto.java

@@ -20,6 +20,8 @@ public class ForwardUpdateDto {
     @NotBlank(message = "转发名称不能为空")
     private String name;
 
+    private Integer tunnelId;
+
     @NotBlank(message = "远程地址不能为空")
     private String remoteAddr;