Setup commercial launch: licenze + backend Cloudflare Worker

Client (Python/JS):
- core/license.py: attivazione, validazione, deactivate (HTTP client + JWT decode)
- core/config.py: campi license_* + URL endpoint + costanti grace/revalidate
- api/bridge.py: get_init_data ritorna license status; activate_license/
  deactivate_license/revalidate_license/open_purchase_page
- check_update riscritto: punta a musictools.djluza.com/api/latest con
  Bearer token, URL di download firmato dal server solo se licensed
- webui: schermata di attivazione bloccante all'avvio; sezione Licenza
  in Impostazioni con verifica/disattiva

Backend (server/):
- Cloudflare Worker + D1 + R2 (vedi server/README.md)
- Endpoints: /api/license/{activate,validate,deactivate}, /api/latest,
  /api/webhook/lemonsqueezy, /api/health
- JWT HS256 con rotazione; max 3 attivazioni/licenza
- Generazione licenze via webhook Lemon Squeezy + email Resend
- Schema D1 in migrations/0001_init.sql

Memory: nuova musictools-commercial-launch.md, rimosso pending obsoleto

NON taggare finche backend non e' deployato (l'app e' bloccante)

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

server/migrations/0001_init.sql

@@ -0,0 +1,42 @@
+-- Schema iniziale licenze MusicTools
+
+CREATE TABLE IF NOT EXISTS licenses (
+  id           INTEGER PRIMARY KEY AUTOINCREMENT,
+  license_key  TEXT NOT NULL UNIQUE,
+  email        TEXT NOT NULL,
+  status       TEXT NOT NULL DEFAULT 'active',  -- active | revoked | refunded
+  source       TEXT,                            -- es. 'lemonsqueezy', 'manual'
+  order_id     TEXT,                            -- id dell'ordine LS
+  created_at   INTEGER NOT NULL,
+  updated_at   INTEGER NOT NULL
+);
+
+CREATE INDEX IF NOT EXISTS idx_licenses_email ON licenses(email);
+
+CREATE TABLE IF NOT EXISTS activations (
+  id           INTEGER PRIMARY KEY AUTOINCREMENT,
+  license_id   INTEGER NOT NULL REFERENCES licenses(id) ON DELETE CASCADE,
+  device_id    TEXT NOT NULL,
+  device_name  TEXT,
+  app_version  TEXT,
+  activated_at INTEGER NOT NULL,
+  last_seen_at INTEGER NOT NULL,
+  revoked_at   INTEGER,
+  UNIQUE (license_id, device_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_activations_license ON activations(license_id);
+
+CREATE TABLE IF NOT EXISTS releases (
+  id           INTEGER PRIMARY KEY AUTOINCREMENT,
+  version      TEXT NOT NULL,
+  platform     TEXT NOT NULL,            -- macos | windows
+  r2_key       TEXT NOT NULL,            -- chiave dentro il bucket R2
+  size_bytes   INTEGER,
+  sha256       TEXT,
+  notes        TEXT,
+  published_at INTEGER NOT NULL,
+  UNIQUE (version, platform)
+);
+
+CREATE INDEX IF NOT EXISTS idx_releases_platform_pub ON releases(platform, published_at DESC);