Refactor .goreleaser.yaml for improved release management and update README with installation instructions

Add script to append release notes and enhance publish-apt.sh for asset downloading

Signed-off-by: Marc Schäfer <git@marcschaeferger.de>

scripts/append-release-notes.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+: "${TAG:?}"
+: "${GHCR_REF:?}"
+: "${DIGEST:?}"
+
+NOTES_FILE="$(mktemp)"
+
+existing_body="$(gh release view "${TAG}" --json body --jq '.body')"
+cat > "${NOTES_FILE}" <<EOF
+${existing_body}
+
+## Container Images
+- GHCR: \`${GHCR_REF}\`
+- Docker Hub: \`${DH_REF:-N/A}\`
+**Digest:** \`${DIGEST}\`
+EOF
+
+gh release edit "${TAG}" --draft --notes-file "${NOTES_FILE}"
+
+rm -f "${NOTES_FILE}"