fix(site): use latest downloads with simpler labels (#398)

Both platform download routes now follow the provider's native latest
attachment: GitHub uses `releases/latest/download/…` and Gitee uses
`releases/download/latest/…`. Publishing a mirrored package no longer
requires rebuilding the website to refresh a version-specific URL.
Remove the build-time release API calls, metadata adapter and its
obsolete tests.

The main buttons read “Download” / “下载”, with “Download via Gitee” /
“Gitee 备用下载” for the alternative. The film's homepage demonstration
inherits the same links and copy. The website guide documents the routes
and the possible delay between primary publication and mirror
completion.

Validation: website build and TypeScript checks; six generated latest
links checked in the homepage and film demonstration; all three real
Gitee latest downloads matched the GitHub package sizes and SHA-256
checksums. The release planner reports `publish: false`.

.github/workflows/website.yml

@@ -1,7 +1,7 @@
 name: Website
 
 on:
-  # Wait for CI/packaging to settle so new downloads reach the same site build.
+  # Publish the website after main's checks complete.
   workflow_run:
     workflows: [CI]
     types: [completed]
@@ -39,35 +39,7 @@ jobs:
           node-version-file: .node-version
           cache: npm
       - run: npm ci
-      - name: Read published downloads
-        env:
-          GH_TOKEN: ${{ github.token }}
-          PIIK_WEBSITE_RELEASE_DATA: ${{ runner.temp }}/website-release.json
-        run: |
-          node --input-type=module <<'JS'
-          import { execFileSync } from 'node:child_process';
-          import { writeFileSync } from 'node:fs';
-          const repository = 'TNTcraftHIM/Piik';
-          const github = JSON.parse(execFileSync('gh', ['api', `repos/${repository}/releases/latest`], { encoding: 'utf8' }));
-          let mirror = null;
-          try {
-            const api = `https://gitee.com/api/v5/repos/${repository}`;
-            const read = async path => {
-              const response = await fetch(api + path, { signal: AbortSignal.timeout(20000) });
-              if (!response.ok) throw new Error(`Mirror metadata: HTTP ${response.status}`);
-              return response.json();
-            };
-            const release = await read(`/releases/tags/${encodeURIComponent(github.tag_name)}`);
-            if (!Number.isSafeInteger(release.id) || release.id <= 0) throw new Error('Invalid mirror release ID');
-            mirror = { ...release, assets: await read(`/releases/${release.id}/attach_files?per_page=100`) };
-          } catch {
-            console.log('Mirror metadata unavailable; keeping the mirror release-page link.');
-          }
-          writeFileSync(process.env.PIIK_WEBSITE_RELEASE_DATA, JSON.stringify({ github, mirror }));
-          JS
       - run: npm run build:website
-        env:
-          PIIK_WEBSITE_RELEASE_DATA: ${{ runner.temp }}/website-release.json
       - uses: actions/configure-pages@v5
       - uses: actions/upload-pages-artifact@v4
         with: