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/_not-found.meta

@@ -0,0 +1,16 @@
+{
+  "status": 404,
+  "headers": {
+    "x-nextjs-stale-time": "300",
+    "x-nextjs-prerender": "1",
+    "x-next-cache-tags": "_N_T_/layout,_N_T_/_not-found/layout,_N_T_/_not-found/page,_N_T_/_not-found"
+  },
+  "segmentPaths": [
+    "/_tree",
+    "/_full",
+    "/_not-found/__PAGE__",
+    "/_not-found",
+    "/_index",
+    "/_head"
+  ]
+}