feat(ci): automated nested PVE provisioning for integration tests

Workflow now provisions a throwaway nested PVE VM via Terraform, runs
integration tests against it, then destroys it. Uses proxmox-auto-install-assistant
to bake the answer file and a first-boot script (installs qemu-guest-agent)
directly into the ISO. IP is discovered via the QEMU guest agent on the
parent PVE, eliminating the need for static IP configuration.

Supports both PVE 8.x and 9.x via workflow_dispatch version selector.
Skip provisioning with skip_provision=true to test against a pre-existing PVE.

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

tests/infrastructure/scripts/prepare-auto-iso.sh

@@ -0,0 +1,38 @@
+#!/usr/bin/env bash
+# Prepare a PVE auto-install ISO with the answer file and first-boot script baked in.
+# Uses --fetch-from iso mode so only a single CD-ROM is needed, no HTTP server required.
+#
+# Usage: prepare-auto-iso.sh <base-iso> <answer-file> [first-boot-script] [output-iso]
+set -euo pipefail
+
+BASE_ISO="$1"
+ANSWER_FILE="$2"
+FIRST_BOOT="${3:-}"
+OUTPUT_ISO="${4:-${BASE_ISO%.iso}-auto.iso}"
+
+for f in "$BASE_ISO" "$ANSWER_FILE"; do
+    if [ ! -f "$f" ]; then
+        echo "ERROR: File not found: $f" >&2
+        exit 1
+    fi
+done
+
+FIRST_BOOT_ARGS=()
+if [ -n "$FIRST_BOOT" ] && [ -f "$FIRST_BOOT" ]; then
+    FIRST_BOOT_ARGS=(--on-first-boot "$FIRST_BOOT")
+fi
+
+echo "Preparing auto-install ISO..."
+echo "  Base ISO:     $BASE_ISO"
+echo "  Answer file:  $ANSWER_FILE"
+echo "  First boot:   ${FIRST_BOOT:-none}"
+echo "  Output:       $OUTPUT_ISO"
+
+proxmox-auto-install-assistant prepare-iso \
+    --fetch-from iso \
+    --answer-file "$ANSWER_FILE" \
+    "${FIRST_BOOT_ARGS[@]}" \
+    --output "$OUTPUT_ISO" \
+    "$BASE_ISO"
+
+echo "Created: $OUTPUT_ISO"