feat(dockerfiles): add bootstrap step for SteamCMD

* Added a `RUN steamcmd +login anonymous +quit || true` command to bootstrap SteamCMD in the Dockerfiles for Ubuntu 20.04, 22.04, and 24.04.
* This ensures that SteamCMD is properly initialized during the image build process.

Dockerfile.ubuntu-2004

@@ -49,5 +49,8 @@ RUN groupadd -g "${PGID}" steam \
 USER steam
 WORKDIR /home/steam
 
+# Bootstrap SteamCMD
+RUN steamcmd +login anonymous +quit || true
+
 ENTRYPOINT ["steamcmd"]
 CMD ["+help", "+quit"]

Dockerfile.ubuntu-2204

@@ -49,5 +49,8 @@ RUN groupadd -g "${PGID}" steam \
 USER steam
 WORKDIR /home/steam
 
+# Bootstrap SteamCMD
+RUN steamcmd +login anonymous +quit || true
+
 ENTRYPOINT ["steamcmd"]
 CMD ["+help", "+quit"]

Dockerfile.ubuntu-2404

@@ -52,5 +52,8 @@ RUN groupadd -g "${PGID}" steam \
 USER steam
 WORKDIR /home/steam
 
+# Bootstrap SteamCMD
+RUN steamcmd +login anonymous +quit || true
+
 ENTRYPOINT ["steamcmd"]
 CMD ["+help", "+quit"]