chore(demo): allow screenshot api url override

docs/DEMO_ACCEPTANCE.md

@@ -40,7 +40,7 @@
 
 1. 从首页开始，左侧菜单依次进入四个页面。
 2. 每页只点上表的路径，停留 2 秒展示“必须看到”的验收文本。
-3. 彩排前运行 `node scripts/capture-demo-screenshots.mjs` 生成四张兜底截图：`/tmp/wygj-ai-interview-flow.png`、`/tmp/wygj-practice-flow.png`、`/tmp/wygj-cases-flow.png`、`/tmp/wygj-sop-flow.png`。
+3. 彩排前运行 `node scripts/capture-demo-screenshots.mjs` 生成四张兜底截图：`/tmp/wygj-ai-interview-flow.png`、`/tmp/wygj-practice-flow.png`、`/tmp/wygj-cases-flow.png`、`/tmp/wygj-sop-flow.png`。如本机 Chrome 或 portless 名称不同，用 `CHROME_BIN=... ADMIN_URL=... API_URL=...` 覆盖。
 4. 若现场网络或浏览器状态异常，直接切上一步生成的截图。
 
 ## 不演示

scripts/capture-demo-screenshots.mjs

@@ -8,6 +8,7 @@ import { spawn } from 'node:child_process';
 
 const root = path.resolve(path.dirname(new URL(import.meta.url).pathname), '..');
 const adminUrl = process.env.ADMIN_URL || 'https://wygj-admin.localhost';
+const apiUrl = process.env.API_URL || adminUrl.replace('wygj-admin', 'wygj-api');
 const outDir = process.argv.includes('--out')
   ? path.resolve(process.argv[process.argv.indexOf('--out') + 1])
   : '/tmp';
@@ -108,7 +109,7 @@ async function login() {
         payload = JSON.stringify(body);
       }
     }
-    const response = await fetch(`${adminUrl.replace('wygj-admin', 'wygj-api')}${endpoint}`, { method, headers, body: payload });
+    const response = await fetch(`${apiUrl}${endpoint}`, { method, headers, body: payload });
     const text = await response.text();
     if (!response.ok) throw new Error(`request failed ${endpoint}: ${response.status}`);
     if (!response.headers.get('encrypt-key')) return JSON.parse(text);