fix: apply review feedback on Docker storage and security documentation

- Fix storage_ip derivation to use default route first, not Swarm RemoteManagers
- Make iSCSI container entrypoint idempotent (check before create for target/LUN/bind)
- Pin erichough/nfs-server from 'latest' to '2.2.1' for reproducibility
- Replace curl|sh Docker install with apt repo in Dockerfile.test
- Add docker.sock security warnings in docker-compose.test.yml and CI workflow
- Update stale 'storage VM' references in comments and .env.test.example"

Co-authored-by: GoodOlClint <151449+GoodOlClint@users.noreply.github.com>
Agent-Logs-Url: https://github.com/GoodOlClint/PSProxmoxVE/sessions/534c0a63-2988-496c-b0ae-e291fcfa050b

tests/Dockerfile.test

@@ -65,5 +65,12 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     && rm -rf /var/lib/apt/lists/*
 
 # Install Docker CLI (for managing storage containers on the host via mounted socket)
-RUN curl -fsSL https://get.docker.com | sh 2>/dev/null \
+RUN install -m 0755 -d /etc/apt/keyrings \
+    && curl -fsSL https://download.docker.com/linux/ubuntu/gpg \
+        | gpg --dearmor -o /etc/apt/keyrings/docker.gpg \
+    && chmod a+r /etc/apt/keyrings/docker.gpg \
+    && echo "deb [arch=amd64 signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu noble stable" \
+        > /etc/apt/sources.list.d/docker.list \
+    && apt-get update \
+    && apt-get install -y --no-install-recommends docker-ce-cli docker-compose-plugin \
     && rm -rf /var/lib/apt/lists/*