Riscrivi backend per hosting Node/MariaDB/PM2 (no Cloudflare)

L'utente ha un hosting Virtualmin esistente (musictools.djluza.com)
con Apache + Node 20 + MariaDB + PM2. Tutta l'infrastruttura
Cloudflare (Workers/D1/R2/Pages) e' rimpiazzata con un backend
Express che gira sul server gia' presente, a costo zero.

Cambia:
- server/src/*.ts (Workers) -> server/src/*.js (Node ESM puro)
- D1 (sqlite) -> MariaDB 10.11 via mysql2/promise
- R2 (storage) -> filesystem locale ~/builds/ + signed URL HMAC
- wrangler.toml -> ecosystem.config.cjs (PM2)
- Aggiunto src/migrate.js: runner SQL idempotente

Endpoints invariati - l'app desktop non vede differenze:
- POST /api/license/{activate,validate,deactivate}
- GET  /api/latest, /api/download
- POST /api/webhook/lemonsqueezy
- GET  /api/health

README riscritto con istruzioni complete: creazione DB,
deploy via rsync/git, config Apache reverse proxy via
Virtualmin, gestione PM2, backup, workflow release.

Email rimane su Resend (deliverability) - free tier sufficiente.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

server/src/server.js

@@ -0,0 +1,62 @@
+import "dotenv/config";
+import express from "express";
+
+import * as license from "./license.js";
+import * as updates from "./updates.js";
+import * as ls from "./lemonsqueezy.js";
+
+const app = express();
+
+// L'app sta dietro Apache reverse proxy: fidati di X-Forwarded-* dal localhost.
+app.set("trust proxy", "loopback");
+app.disable("x-powered-by");
+
+// CORS minimale (solo per /api/*)
+app.use("/api", (req, res, next) => {
+  res.set("Access-Control-Allow-Origin", "*");
+  res.set("Access-Control-Allow-Methods", "GET,POST,OPTIONS");
+  res.set("Access-Control-Allow-Headers", "Content-Type,Authorization");
+  if (req.method === "OPTIONS") return res.status(204).end();
+  next();
+});
+
+// Health check (no body parser necessario)
+app.get("/api/health", (_req, res) => {
+  res.json({ ok: true, version: process.env.LATEST_VERSION || "" });
+});
+
+// WEBHOOK Lemon Squeezy: deve ricevere il body RAW per verificare la firma.
+// Va registrato PRIMA del json parser globale.
+app.post(
+  "/api/webhook/lemonsqueezy",
+  express.raw({ type: "application/json", limit: "1mb" }),
+  ls.webhook,
+);
+
+// JSON parser per tutti gli altri endpoint
+app.use(express.json({ limit: "128kb" }));
+
+// Licenze
+app.post("/api/license/activate",   license.activate);
+app.post("/api/license/validate",   license.validate);
+app.post("/api/license/deactivate", license.deactivate);
+
+// Aggiornamenti + download firmato
+app.get("/api/latest",   updates.latest);
+app.get("/api/download", updates.download);
+
+// 404 JSON solo per /api/*
+app.use("/api", (_req, res) => res.status(404).json({ error: "Not found" }));
+
+// Error handler
+app.use((err, _req, res, _next) => {
+  console.error("[unhandled]", err);
+  if (res.headersSent) return;
+  res.status(500).json({ error: "Internal error" });
+});
+
+const PORT = Number(process.env.PORT || 4002);
+const HOST = process.env.HOST || "127.0.0.1";
+app.listen(PORT, HOST, () => {
+  console.log(`[musictools-api] listening on ${HOST}:${PORT}`);
+});