move build to buildscript since in docker build folders are not mapped

docker-compose.yaml

@@ -10,6 +10,7 @@ services:
     user: "1000:1000"
     tty: true
     stdin_open: true
+    command: bash /home/builduser/build.sh
     volumes:
       # Firmware outputs mapped directly to host filesystem
       - ./bin:/home/builduser/openwrt/bin
@@ -17,6 +18,8 @@ services:
       - ./dl:/home/builduser/openwrt/dl
       # Persistent build configuration file (.config)
       - ./.config:/home/builduser/openwrt/.config
+      # build script
+      - ./build.sh:/home/builduser/build.sh
       # Named volumes for heavy build artifacts (maximizes I/O performance)
       - openwrt-build-dir:/home/builduser/openwrt/build_dir
       - openwrt-staging-dir:/home/builduser/openwrt/staging_dir