fix: inject linux-musl sharp binaries into build/ to fix 502 on Dokploy

build.sh runs npm run build on macOS, so only the host's sharp binary
(darwin-arm64) got traced into the standalone output. The container
runs node:20-alpine (Linux, musl libc), which cannot load that binary
- the server crashed at runtime, causing a 502 even though the docker
build itself succeeded.

npm pack can fetch another platform's prebuilt sharp/libvips tarballs
without an install-time OS check, so build.sh now pulls the
linux-musl x64 and arm64 builds directly into build/node_modules and
drops the now-unused host binary.

build/.next/server/app/sitemap.xml.meta

@@ -0,0 +1 @@
+{"status":200,"headers":{"cache-control":"public, max-age=0, must-revalidate","content-type":"application/xml","x-next-cache-tags":"_N_T_/layout,_N_T_/sitemap.xml/layout,_N_T_/sitemap.xml/route,_N_T_/sitemap.xml"}}