feat(server+web): 客户端下载闭环——pangolin-server /downloads + 官网下载链接

- server: /downloads/* 公开静态服务(NewDownloadsHandler,DOWNLOADS_DIR 默认
  /var/lib/pangolin/downloads),防目录穿越/不列目录/缺目录不崩,Cache-Control:
  no-cache 保证 CI 覆盖后永远最新。挂在 /healthz 同级(免鉴权)。含 4 项测试。
- deploy.sh: install -d 下载目录 + server.env 注入 DOWNLOADS_DIR。
- web: site.ts 增 downloads.{android,windows}(→ https://api.yanmeiai.com/downloads/*);
  Download.astro 接上 Android/Windows 按钮,iOS/macOS/Linux 改「即将推出」禁用态。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013nMthbVEmQquxBRKb9Fj8u

web/website/src/components/Download.astro

@@ -1,15 +1,17 @@
 ---
 import Icon from './Icon.astro';
 import type { T } from '../i18n/strings';
+import { SITE } from '../config/site';
 
 interface Props { t: T }
 const { t } = Astro.props;
 
-const plats = [
+// href 缺省 = 本轮未接入下载（iOS / macOS / Linux），按钮渲染为禁用态占位。
+const plats: { icon: string; name: string; ver: string; href?: string }[] = [
   { icon: 'smartphone', name: 'iOS', ver: 'iOS 16+' },
-  { icon: 'smartphone', name: 'Android', ver: 'Android 9+' },
+  { icon: 'smartphone', name: 'Android', ver: 'Android 9+', href: SITE.downloads.android },
   { icon: 'laptop', name: 'macOS', ver: 'macOS 12+' },
-  { icon: 'monitor', name: 'Windows', ver: 'Win 10/11' },
+  { icon: 'monitor', name: 'Windows', ver: 'Win 10/11', href: SITE.downloads.windows },
   { icon: 'terminal', name: 'Linux', ver: 'deb / rpm' },
 ];
 ---
@@ -26,7 +28,11 @@ const plats = [
           <div class="ico"><Icon name={p.icon} /></div>
           <div class="pn">{p.name}</div>
           <div class="pv">{p.ver}</div>
-          <a class="gb"><Icon name="download" /><span>{t('dl.get')}</span></a>
+          {p.href ? (
+            <a class="gb" href={p.href}><Icon name="download" /><span>{t('dl.get')}</span></a>
+          ) : (
+            <span class="gb disabled" aria-disabled="true"><Icon name="download" /><span>{t('dl.soon')}</span></span>
+          )}
         </div>
       ))}
     </div>