Server bundle 按需编译

### Summary | 概述

Weex 下已经完全与 Server bundle 构建解耦了，考虑加开关可以不构建该产物。

### Motivation | 背景

Weex 下已经完全与 Server bundle 构建解耦了，考虑加开关可以不构建该产物。

### Usage example | 使用示例

_No response_

### Detailed design | 方案设计

Weex 下已经完全与 Server bundle 构建解耦了，考虑加开关可以不构建该产物。

### Additional context | 额外信息

_No response_

No files, tests, or entry points are named in the issue. First locate the Server bundle build configuration and existing Weex/build separation, then determine how an opt-out switch should be exposed and verify that disabling it skips the Server bundle while the default build remains unchanged.

Written by the indexing model from the issue text.