feat(ci): unify CI and local integration test infrastructure

- Replace tests/infrastructure/Dockerfile with tests/Dockerfile.test
  (single multi-stage Dockerfile for both CI and local dev)
- CI container-image job now builds from Dockerfile.test target dev-infra
- Add ARM support: PowerShell installed via dotnet tool on arm64,
  APT package on amd64
- Replace tests/dev.sh (bash) with tests/dev.ps1 (PowerShell) for
  cross-platform support (Windows, macOS, Linux)
- Add -DockerHost parameter for running x86 containers on a remote
  Docker host from ARM Macs (rsyncs repo, uses SSH Docker transport)
- Add -NoCleanup switch to keep nested PVE VMs after integration tests
- integration command now provisions nested PVE VMs instead of testing
  against a pre-existing PVE directly
- Share /opt/pve-isos host path between CI and local dev (was separate
  Docker named volume)
- Delete tools/Invoke-Tests.ps1 (unused, overlapped with run-integration.sh)
- Add .gitignore entries for Terraform state/artifacts
- Update all documentation references

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

tests/infrastructure/Dockerfile

@@ -1,67 +0,0 @@
-FROM ubuntu:24.04
-
-ENV DEBIAN_FRONTEND=noninteractive
-
-# ── Base packages ──────────────────────────────────────────────────────
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    curl \
-    jq \
-    dosfstools \
-    mtools \
-    openssh-client \
-    sshpass \
-    apt-transport-https \
-    gnupg \
-    lsb-release \
-    ca-certificates \
-    python3 \
-    xorriso \
-    && rm -rf /var/lib/apt/lists/*
-
-# ── Microsoft repo (PowerShell) ───────────────────────────────────────
-RUN curl -fsSL https://packages.microsoft.com/keys/microsoft.asc \
-    | gpg --dearmor -o /usr/share/keyrings/microsoft-archive-keyring.gpg && \
-    echo "deb [arch=amd64 signed-by=/usr/share/keyrings/microsoft-archive-keyring.gpg] \
-    https://packages.microsoft.com/ubuntu/24.04/prod noble main" \
-    > /etc/apt/sources.list.d/microsoft-prod.list
-
-# ── HashiCorp repo (Terraform) ────────────────────────────────────────
-RUN curl -fsSL https://apt.releases.hashicorp.com/gpg \
-    | gpg --dearmor -o /usr/share/keyrings/hashicorp-archive-keyring.gpg && \
-    echo "deb [arch=amd64 signed-by=/usr/share/keyrings/hashicorp-archive-keyring.gpg] \
-    https://apt.releases.hashicorp.com noble main" \
-    > /etc/apt/sources.list.d/hashicorp.list
-
-# ── Proxmox repo (proxmox-auto-install-assistant) ─────────────────────
-RUN curl -fsSL https://enterprise.proxmox.com/debian/proxmox-release-bookworm.gpg \
-    -o /usr/share/keyrings/proxmox-release-bookworm.gpg && \
-    echo "deb [signed-by=/usr/share/keyrings/proxmox-release-bookworm.gpg] \
-    http://download.proxmox.com/debian/pve bookworm pve-no-subscription" \
-    > /etc/apt/sources.list.d/proxmox-pve.list
-
-# ── Install tooling ───────────────────────────────────────────────────
-RUN apt-get update && apt-get install -y --no-install-recommends \
-    powershell \
-    terraform \
-    proxmox-auto-install-assistant \
-    qemu-utils \
-    && rm -rf /var/lib/apt/lists/*
-
-# ── Install Pester ────────────────────────────────────────────────────
-RUN pwsh -NoProfile -Command \
-    'Set-PSRepository -Name PSGallery -InstallationPolicy Trusted; \
-     Install-Module -Name Pester -MinimumVersion 5.0 -Scope AllUsers -Force'
-
-# ── Verify all tools are present ──────────────────────────────────────
-RUN echo "=== Tool verification ===" && \
-    pwsh --version && \
-    terraform --version && \
-    proxmox-auto-install-assistant --version && \
-    sshpass -V | head -1 && \
-    xorriso --version 2>&1 | head -1 && \
-    qemu-img --version | head -1 && \
-    curl --version | head -1 && \
-    jq --version && \
-    python3 --version && \
-    ssh -V 2>&1 && \
-    echo "=== All tools verified ==="