feat(checksum): add checksum support to download components and update workflow

- Enhanced ButtonCard component to accept and display SHA-256 checksums.
- Updated PlatformDownload and release-data to include checksum information for each release.
- Modified DownloadScript to apply twilight mode to new checksum buttons.
- Adjusted download page to retrieve and display checksums dynamically.

src/utils/githubChecksums.ts

@@ -0,0 +1,31 @@
+/**
+ * Fetches the latest release notes from GitHub and parses the SHA-256 checksums.
+ * Returns a mapping from filename to checksum.
+ */
+export async function getChecksums() {
+  const token = import.meta.env.GITHUB_TOKEN;
+  if (!token) throw new Error('GITHUB_TOKEN is not set in environment variables');
+
+  const res = await fetch('https://api.github.com/repos/zen-browser/desktop/releases/latest', {
+    headers: {
+      'Accept': 'application/vnd.github+json',
+      'Authorization': `Bearer ${token}`,
+      'X-GitHub-Api-Version': '2022-11-28',
+      'User-Agent': 'zen-browser-checksum-fetcher',
+    },
+  });
+  if (!res.ok) throw new Error('Failed to fetch GitHub release: ' + res.statusText);
+  const data = await res.json();
+  const body = data.body as string;
+
+  // Extract the checksum block
+  const match = body.match(/File Checksums \(SHA-256\)[\s\S]*?```([\s\S]*?)```/);
+  const checksums: Record<string, string> = {};
+  if (match && match[1]) {
+    match[1].split('\n').forEach(line => {
+      const [hash, filename] = line.trim().split(/\s+/, 2);
+      if (hash && filename) checksums[filename] = hash;
+    });
+  }
+  return checksums;
+}