also cache astro files

nixpacks.json

@@ -0,0 +1,27 @@
+{
+  "variables": {
+    "CI": "true",
+    "NIXPACKS_METADATA": "node",
+    "NODE_ENV": "production",
+    "NPM_CONFIG_PRODUCTION": "false"
+  },
+  "phases": {
+    "build": {
+      "dependsOn": ["install"],
+      "cmds": ["pnpm run build"],
+      "cacheDirectories": ["node_modules/.cache", "node_modules/.astro"]
+    },
+    "install": {
+      "dependsOn": ["setup"],
+      "cmds": ["npm install -g corepack@0.24.1 && corepack enable", "pnpm i --frozen-lockfile"],
+      "cacheDirectories": ["/root/.local/share/pnpm/store/v3"],
+      "paths": ["/app/node_modules/.bin"]
+    },
+    "setup": {
+      "nixPkgs": ["nodejs_22"]
+    }
+  },
+  "start": {
+    "cmd": "pnpm run preview"
+  }
+}