feat(ci): multi-node PVE provisioning and Docker-based shared storage

Provision two PVE nodes per version (a/b) for future cluster testing,
plus Docker-based iSCSI target and NFS server for shared storage tests.

Multi-node changes:
- Each PVE version gets two nodes: 9a/9b and 8a/8b (4 VMs total)
- Parameterized answer.toml FQDN for unique hostnames per node
- Per-node auto-install ISOs with unique answer files
- Node name discovered from FQDN and included in test config
- API token creation handles pre-existing tokens (delete + recreate)
- New test env vars: PVETEST_HOST_B, PVETEST_APITOKEN_B
- Removed preflight cleanup from provision (use explicit cleanup instead)

Docker storage services:
- New docker-compose.storage.yml with iSCSI (tgt) and NFS containers
- Host networking so PVE nodes can reach storage services
- Docker socket mounted into dev-infra container for host Docker access
- Docker CLI added to dev-infra Dockerfile stage
- New test env vars: PVETEST_STORAGE_VM_IP, PVETEST_ISCSI_IQN, PVETEST_NFS_EXPORT

Other fixes:
- first-boot.sh installs open-iscsi on PVE nodes
- preflight-cleanup.sh handles empty ISO filename gracefully
- TMPDIR set to work dir to avoid /tmp overflow during ISO uploads

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/integration-tests.yml

@@ -102,12 +102,12 @@ jobs:
           push: true
           tags: ${{ env.TEST_IMAGE }}:${{ github.sha }},${{ env.TEST_IMAGE }}:latest
 
-  # ── Provision all nested PVE VMs (self-hosted) ──────────────────────
+  # ── Provision all nested PVE VMs + storage VM (self-hosted) ─────────
   provision:
     if: inputs.skip_provision != true
     needs: [build, container-image]
     runs-on: [self-hosted, proxmox, integration]
-    timeout-minutes: 30
+    timeout-minutes: 45
     container:
       image: ghcr.io/goodolclint/psproxmoxve-integration:${{ github.sha }}
       credentials:
@@ -115,6 +115,7 @@ jobs:
         password: ${{ secrets.GITHUB_TOKEN }}
       volumes:
         - /opt/pve-isos:/opt/pve-isos
+        - /var/run/docker.sock:/var/run/docker.sock
 
     steps:
       - uses: actions/checkout@v6
@@ -185,6 +186,7 @@ jobs:
         password: ${{ secrets.GITHUB_TOKEN }}
       volumes:
         - /opt/pve-isos:/opt/pve-isos
+        - /var/run/docker.sock:/var/run/docker.sock
 
     steps:
       - uses: actions/checkout@v6