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-linuxmusl-x64/package.json

@@ -0,0 +1,46 @@
+{
+  "name": "@img/sharp-linuxmusl-x64",
+  "version": "0.34.5",
+  "description": "Prebuilt sharp for use with Linux (musl) x64",
+  "author": "Lovell Fuller <npm@lovell.info>",
+  "homepage": "https://sharp.pixelplumbing.com",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/lovell/sharp.git",
+    "directory": "npm/linuxmusl-x64"
+  },
+  "license": "Apache-2.0",
+  "funding": {
+    "url": "https://opencollective.com/libvips"
+  },
+  "preferUnplugged": true,
+  "optionalDependencies": {
+    "@img/sharp-libvips-linuxmusl-x64": "1.2.4"
+  },
+  "files": [
+    "lib"
+  ],
+  "publishConfig": {
+    "access": "public"
+  },
+  "type": "commonjs",
+  "exports": {
+    "./sharp.node": "./lib/sharp-linuxmusl-x64.node",
+    "./package": "./package.json"
+  },
+  "engines": {
+    "node": "^18.17.0 || ^20.3.0 || >=21.0.0"
+  },
+  "config": {
+    "musl": ">=1.2.2"
+  },
+  "os": [
+    "linux"
+  ],
+  "libc": [
+    "musl"
+  ],
+  "cpu": [
+    "x64"
+  ]
+}