fix: Address linting issues in rootless Docker implementation

- Add --no-install-recommends to apt-get install in Dockerfile
- Consolidate consecutive RUN instructions in Dockerfile
- Fix shellcheck warnings: quote variables and use -n instead of \! -z
- These changes improve best practices without affecting functionality

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

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

docker/Dockerfile.rootless

@@ -1,7 +1,7 @@
 # build rcon client
 FROM debian:stable-slim AS rcon-builder
 RUN apt-get -q update \
-    && DEBIAN_FRONTEND=noninteractive apt-get -qy install build-essential
+    && DEBIAN_FRONTEND=noninteractive apt-get -qy install build-essential --no-install-recommends
 
 WORKDIR /src
 COPY rcon/ /src
@@ -78,11 +78,9 @@ COPY files/docker-entrypoint-rootless.sh /docker-entrypoint.sh
 COPY files/config.ini /opt/factorio/config/config.ini
 COPY --from=rcon-builder /src/rcon /bin/rcon
 
-# Make all scripts executable
-RUN chmod +x /*.sh
-
-# Set proper permissions for the factorio directory
-RUN chmod -R 777 /opt/factorio /factorio
+# Make all scripts executable and set proper permissions for the factorio directory
+RUN chmod +x /*.sh \
+    && chmod -R 777 /opt/factorio /factorio
 
 VOLUME /factorio
 EXPOSE $PORT/udp $RCON_PORT/tcp

docker/files/docker-entrypoint-rootless.sh

@@ -44,11 +44,11 @@ fi
 
 # Update mods if requested
 if [[ ${UPDATE_MODS_ON_START:-} == "true" ]]; then
-  ${INSTALLED_DIRECTORY}/docker-update-mods.sh
+  "${INSTALLED_DIRECTORY}"/docker-update-mods.sh
 fi
 
 # Handle DLC
-${INSTALLED_DIRECTORY}/docker-dlc.sh
+"${INSTALLED_DIRECTORY}"/docker-dlc.sh
 
 # In rootless mode, we don't need to handle user switching or chown
 # The container runs as the specified user from the start
@@ -76,7 +76,7 @@ if [[ $GENERATE_NEW_SAVE == true ]]; then
     if [[ -f "$SAVES/$SAVE_NAME.zip" ]]; then
         echo "Map $SAVES/$SAVE_NAME.zip already exists, skipping map generation"
     else
-        if [[ ! -z "$PRESET" ]]; then
+        if [[ -n "$PRESET" ]]; then
             $EXEC /opt/factorio/bin/x64/factorio \
                 --create "$SAVES/$SAVE_NAME.zip" \
                 --preset "$PRESET" \