chore: monorepo - plugin, backend und hilfsdaten in einem repo

- Eltern-Ordner ist jetzt EIN Git-Repo (statt getrennter Repos).
- root .gitignore haelt Secrets (.env), node_modules, DB und Build-Artefakte raus.
- release.ps1: manueller Release (ZIP bauen + ans Backend laden).
- root README mit Struktur und Release-Ablauf.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

license-backend/package.json

@@ -0,0 +1,22 @@
+{
+  "name": "license-backend",
+  "version": "1.0.0",
+  "description": "Self-hosted license server for WordPress plugins (extensible, multi-product).",
+  "author": "Lucas Orth",
+  "license": "UNLICENSED",
+  "private": true,
+  "type": "module",
+  "main": "src/server.js",
+  "scripts": {
+    "start": "node src/server.js",
+    "test:unit": "node test/util.test.mjs && node test/scan.test.mjs",
+    "test:integration": "node --import ./test/register.mjs ./test/integration.mjs"
+  },
+  "engines": {
+    "node": ">=20"
+  },
+  "dependencies": {
+    "better-sqlite3": "^11.3.0",
+    "express": "^4.21.0"
+  }
+}