feat(env): 新增环境识别，网关地址按环境自动切换

- 新增 utils/env，用 wx.getAccountInfoSync().miniProgram.envVersion 识别 develop/trial/release
- request 与 lefu 的地址由硬编码改为按环境映射，develop/trial 走测试网关，release 走正式网关

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

miniprogram/utils/env/index.ts

@@ -0,0 +1,12 @@
+import type { EnvType } from './types'
+
+export type { EnvType }
+
+/** 获取当前运行环境，基础库不支持 getAccountInfoSync 时回退 develop */
+export const ENV: EnvType = (() => {
+    try {
+        return wx.getAccountInfoSync().miniProgram.envVersion as EnvType
+    } catch {
+        return 'develop'
+    }
+})()

miniprogram/utils/env/types.ts

@@ -0,0 +1,2 @@
+/** 小程序运行环境：develop 开发版 / trial 体验版 / release 正式版 */
+export type EnvType = 'develop' | 'trial' | 'release'