fix(web): release-download proxy points at this repo's GitHub releases

The npm postinstall downloads the platform binary through
levelcode.vercel.app/api/releases/download/... which redirected to
github.com/yethikrishna/levelcode-community — a repo that doesn't
carry our releases, so every fresh install 404'd after publishing.
Now defaults to yethikrishna/levelcode/releases with a
LEVELCODE_RELEASES_BASE_URL env override for forks.

Author: yethikrishna

web/src/app/api/releases/download/[version]/[filename]/route.ts

@@ -18,7 +18,12 @@ export async function GET(
   }
 
   // Current download location - can be changed in the future without affecting old clients
-  const downloadUrl = `https://github.com/yethikrishna/levelcode-community/releases/download/v${version}/${filename}`
+  // Env-overridable so forks/self-hosted deploys can repoint without code edits.
+  // Defaults to this repository's GitHub releases.
+  const releasesBase =
+    process.env.LEVELCODE_RELEASES_BASE_URL ||
+    'https://github.com/yethikrishna/levelcode/releases/download'
+  const downloadUrl = `${releasesBase}/v${version}/${filename}`
 
   return NextResponse.redirect(downloadUrl, 302)
 }