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/node_modules/@img/sharp-libvips-linuxmusl-arm64/package.json

@@ -0,0 +1,42 @@
+{
+  "name": "@img/sharp-libvips-linuxmusl-arm64",
+  "version": "1.2.4",
+  "description": "Prebuilt libvips and dependencies for use with sharp on Linux (musl) 64-bit ARM",
+  "author": "Lovell Fuller <npm@lovell.info>",
+  "homepage": "https://sharp.pixelplumbing.com",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/lovell/sharp-libvips.git",
+    "directory": "npm/linuxmusl-arm64"
+  },
+  "license": "LGPL-3.0-or-later",
+  "funding": {
+    "url": "https://opencollective.com/libvips"
+  },
+  "preferUnplugged": true,
+  "publishConfig": {
+    "access": "public"
+  },
+  "files": [
+    "lib",
+    "versions.json"
+  ],
+  "type": "commonjs",
+  "exports": {
+    "./lib": "./lib/index.js",
+    "./package": "./package.json",
+    "./versions": "./versions.json"
+  },
+  "config": {
+    "musl": ">=1.2.2"
+  },
+  "os": [
+    "linux"
+  ],
+  "libc": [
+    "musl"
+  ],
+  "cpu": [
+    "arm64"
+  ]
+}