feat: initial commit — local services (backend + manager dashboard + waiter PWA)

Includes all work to date:
- local_backend: FastAPI backend with products, orders, tables, shifts, cloud sync
- manager_dashboard: React manager UI with product/category management, reports, settings
- waiter_pwa: React PWA for waiter devices
- Category reparent endpoint and UI
- Waiter domain: local_ip sent on heartbeat, waiter_domain persisted from cloud response
- QR code modal in AppInfoTab for waiter domain
- Product form: number input spinners removed, category pre-selected on new product
- Category row: count badge moved to far right

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.env.example

@@ -0,0 +1,14 @@
+# Registry
+REGISTRY=registry.yourdomain.com
+VERSION=1.0.0
+
+# Backend runtime secrets (get SITE_ID and SITE_KEY from sysadmin panel)
+SITE_ID=your-site-id
+SITE_KEY=your-site-key
+CLOUD_URL=https://api.yourdomain.com
+SECRET_KEY=generate-with-openssl-rand-hex-32
+LICENSE_GRACE_HOURS=24
+
+# Volumes — absolute paths recommended on client machines
+DATA_PATH=/home/user/appdata/pos/data
+LOGO_PATH=/home/user/appdata/pos/logo.png