Refactor Dockerfiles for Gitea runners: streamline package installations, remove unnecessary dependencies, and ensure non-root execution

ansible/files/dockerfiles/linux-runners/Dockerfile.cpp-build

@@ -1,19 +1,11 @@
 FROM local/gitea-runner-base:latest
 
-# cpp-build runner profile: dedicated C/C++ build environment.
+# Base image sets USER runner; switch back to root for package installs
 USER root
 RUN apt-get update && apt-get install -y --no-install-recommends \
 	build-essential \
-	ca-certificates \
 	cmake \
-	curl \
-	git \
-	jq \
-	make \
-	openssh-client \
-	python3 \
-	python3-pip \
-	rsync \
-	unzip \
-	zip \
 	&& rm -rf /var/lib/apt/lists/*
+
+# Default to non-root execution
+USER runner