Fix ARM64 emulation support in all entrypoints

- Add shared setup-exec.sh script to handle ARM64 emulation logic
- Update scenario.sh and scenario2map.sh to use box64 emulation on ARM64
- Refactor docker-entrypoint.sh and docker-entrypoint-rootless.sh to use shared script
- Ensures all factorio binary calls work correctly on ARM64 platforms

Fixes #585

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

docker/files/scenario2map.sh

@@ -1,5 +1,6 @@
 #!/bin/bash
 set -eoux pipefail
+INSTALLED_DIRECTORY=$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")
 
 if [[ -z ${1:-} ]]; then
   echo "No argument supplied"
@@ -23,5 +24,9 @@ if [[ ! -f $CONFIG/map-settings.json ]]; then
   cp /opt/factorio/data/map-settings.example.json "$CONFIG/map-settings.json"
 fi
 
-exec /opt/factorio/bin/x64/factorio \
+# Setup ARM64 emulation support
+EXEC=""
+source "${INSTALLED_DIRECTORY}/setup-exec.sh"
+
+exec $EXEC /opt/factorio/bin/x64/factorio \
   --scenario2map "$SERVER_SCENARIO"