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/middleware-manifest.json

@@ -0,0 +1,6 @@
+{
+  "version": 3,
+  "middleware": {},
+  "sortedMiddleware": [],
+  "functions": {}
+}