feat: plugin skeleton for Shopware 6.6 and 6.7 with CI and release pipeline

- composer.json (MIT, shopware/core ~6.6.0 || ~6.7.0, PHP ^8.2), plugin class, placeholder icon
- PR checks and release workflow taken over from AeonDumpManager; phpunit runs as a 6.6/6.7 matrix
- CHANGELOG, LICENSE, README, CLAUDE.md, smoke test

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/ci/assert-built-assets.sh

@@ -0,0 +1,17 @@
+#!/usr/bin/env bash
+# Assert that a packaged extension zip contains the built admin/storefront JS when the sources exist.
+# Usage: scripts/ci/assert-built-assets.sh <zip>   (run from the repo root; BusyBox-safe: uses unzip -l)
+set -euo pipefail
+ZIP="${1:?usage: assert-built-assets.sh <zip>}"
+LIST=$(unzip -l "$ZIP")
+
+check() { # <label> <entry-glob-prefix> <expected path in zip>
+  local label="$1" entry="$2" expected="$3"
+  if [ -f "${entry}/main.js" ] || [ -f "${entry}/main.ts" ]; then
+    echo "$LIST" | grep -q "$expected" || { echo "::error::${label} entry exists but the zip has no built ${label} JS (${expected})"; exit 1; }
+    echo "ok: ${label} JS is in the zip"
+  fi
+}
+
+check admin src/Resources/app/administration/src "Resources/public/administration/assets/"
+check storefront src/Resources/app/storefront/src "Resources/app/storefront/dist/"