chore(release): archive ISO build recipes, tarball-only releases

Releases no longer ship as bootable ISOs. Archipelago updates are
distributed as the backend binary plus a frontend tarball referenced by
releases/manifest.json. Nodes OTA-update via scripts/self-update.sh.

Filebrowser and AIUI remain bundled inside the frontend tarball and
deployed atomically, verified present in v1.7.43-alpha release artifact
(189 AIUI files, filebrowser-client bundle).

Archived under image-recipe/_archived/ (resurrectable if ISO distribution
is reintroduced):
  - build-auto-installer-iso.sh
  - build-unbundled-iso.sh
  - test-iso-qemu.sh
  - scripts/convert-iso-to-disk.sh
  - BUILD-ISO-STATUS.md, ISO-BUILD-CHECKLIST.md
  - branding/isohdpfx.bin
  - .gitea/workflows/build-iso-dev.yml

Updated release process docs to drop ISO references:
  - scripts/create-release.sh (next-steps text)
  - docs/BETA-RELEASE-CHECKLIST.md
  - docs/hotfix-process.md
  - README.md

image-recipe/_archived/scripts/convert-iso-to-disk.sh

@@ -0,0 +1,65 @@
+#!/bin/bash
+# Convert ISO image to bootable disk image
+# Creates a raw disk image that can be flashed directly
+
+set -e
+
+OUTPUT_DIR="${1:-../results}"
+ARCHIPELAGO_VERSION="${ARCHIPELAGO_VERSION:-0.1.0}"
+ARCH="${ARCH:-x86_64}"
+
+echo "💾 Converting ISO to disk image..."
+
+# Find ISO file
+ISO_FILE=$(ls "$OUTPUT_DIR"/*.iso 2>/dev/null | head -1)
+if [ -z "$ISO_FILE" ]; then
+    echo "❌ No ISO file found in $OUTPUT_DIR"
+    exit 1
+fi
+
+echo "   Source ISO: $ISO_FILE"
+
+# Create disk image (4GB minimum)
+DISK_SIZE=4096  # 4GB in MB
+DISK_IMG="$OUTPUT_DIR/archipelago-${ARCHIPELAGO_VERSION}-${ARCH}.img"
+
+echo "   Creating disk image: $DISK_IMG"
+
+# Check if we have required tools
+if ! command -v dd >/dev/null 2>&1; then
+    echo "❌ dd not found"
+    exit 1
+fi
+
+# Create empty disk image
+dd if=/dev/zero of="$DISK_IMG" bs=1M count=$DISK_SIZE 2>/dev/null || {
+    echo "❌ Failed to create disk image"
+    exit 1
+}
+
+# Note: Full disk image creation with partitions requires:
+# - parted or fdisk
+# - mkfs.vfat, mkfs.ext4
+# - losetup (Linux only)
+# - grub-install
+
+# For now, we'll create a simple approach:
+# The ISO can be used directly, or users can use tools like:
+# - balenaEtcher (macOS/Linux GUI)
+# - Rufus (Windows)
+# - dd (command line)
+
+echo "⚠️  Full disk image conversion requires additional tools"
+echo "   For now, use the ISO file directly with:"
+echo "   - balenaEtcher (recommended)"
+echo "   - dd command (see docs)"
+echo ""
+echo "   ISO file: $ISO_FILE"
+echo "   Size: $(du -h "$ISO_FILE" | cut -f1)"
+
+# Clean up empty image file
+rm -f "$DISK_IMG"
+
+echo ""
+echo "💡 Tip: Use the ISO file with a USB flashing tool"
+echo "   The ISO is bootable and can be flashed directly"