fix(delivery): deliver orders with father-articles and no-payment orders

- Treat an article that has become a father (nIstVater=1) as a free
  position (kArtikel=0) with the name kept: VersandIntern.vBestellPosOffen
  joins tArtikel with nIstVater=0, so such positions could never be
  reserved and failed with "insufficient stock after POS shortage
  booking" (e.g. Becks 42000030).
- Recalculate tAuftragPositionEckdaten before deliverOrder so orders
  without payments get their positions reserved too (previously only
  insertPayment triggered the recalculation).

Also adds debug logging across the delivery pipeline (reserve, commit,
deliver, session, stock-shortage, create-order).

.env.example

@@ -1,7 +1,14 @@
 # HTTPS POS server
 PORT=4443
+
+# Plain HTTP POS server (no TLS) - same API, unencrypted
+HTTP_PORT=8087
+
 AUTH_TOKEN=df40ad2067954646abb0499548a52241
 PAIRING_CODE=307018
+
+# Allow generating fresh pairing codes on demand via GET /v1/newpin (default: false)
+NEWPIN_ENABLED=false
 LOG_FILE=logs/requests.log
 ORDER_LOG_FILE=logs/orders.log