fix: allow HTTP for configurable service endpoints

DeepSeek Harness and Weixin binding configuration rejected non-loopback HTTP endpoints even when users explicitly selected those internal services. Configurable endpoints now accept valid HTTP and HTTPS URLs without host-location restrictions, while retaining the required protocol and API-key checks.

Release note: 模型连接、DeepSeek Harness 与微信绑定现在可直接使用局域网或公网 HTTP/HTTPS 服务地址，不再强制公网 HTTPS 或本机回环地址。

src/main/channels/channel-settings-store.test.ts

@@ -231,7 +231,7 @@ describe('ChannelSettingsStore', () => {
     const bound = await store.saveWeixinBinding({
       accountId: 'account-123456',
       userId: 'user-654321',
-      baseUrl: 'https://ilinkai.weixin.qq.com',
+      baseUrl: 'http://ilinkai.weixin.qq.com',
       token: 'weixin-private-token'
     })
     expect(bound.weixin).toMatchObject({