Optical QC control: QiTech Control library and shop

User, 19 Oct 2026: check github.com/qitechgmbh/control and
shop.qitech.de/collections/ethercat.

- QiTech Control (LGPL-3.0, Rust on an EtherCrab fork, NixOS, runs
  QiTech's own machines): plan now uses its EtherCAT library qitech_lib,
  pinned, as the layer under our station service; not the full Electron
  app. It has DC SYNC0, SDO/PDO handling, EK1100/EL2809/EL3021/EL3024
  drivers and a CiA402 MINAS A6 servo driver to copy for the A6-EC.
  Drivers to write: EK1101, EL1809, EL3152, EL5101, A6-EC (upstream).
  Kernel: start from QiTech's tested settings (6.18, preempt=full,
  isolcpus 2,3); 6.12 PREEMPT_RT stays the fallback for IgH.
- QiTech shop (new Beckhoff stock from an insolvency, ships worldwide):
  EK1101 EUR 85.13, EL1809 EUR 16.53, EL2809 EUR 41.03, EL9011 EUR 1.76
  replace the geizhals offers, EUR 207.57 less. TwinSAFE and Beckhoff
  STO servo terminals noted, not taken.
- EtherCAT parts EUR 1,684 to 1,897 + 2 servo kits (THB 72k to 80k);
  bench parts about THB 56k; spare coupler/DI/DO now stocked.
- BOM total USD 16,671 to 32,681 (THB 0.55M to 1.08M).

README.md

@@ -189,8 +189,9 @@ The detail lives in dedicated documents:
   rim-belt conveyor, chuck, sensors) with a sourced bill of materials
 - [QC station control plan](docs/equipment/inline-qc-control-plan.md):
   EtherCAT with two 100 W servo kits, Beckhoff I/O and an N100 mini PC
-  running an open-source master on NixOS; bus layout, I/O list,
-  geizhals.de prices, safety circuit, bench test and build order
+  running QiTech's open-source EtherCAT library on NixOS; bus layout, I/O
+  list, geizhals.de and QiTech shop prices, safety circuit, bench test and
+  build order
 - [Quality automation](docs/quality-automation.md): stamper metrology
   (Keyence-class confocal, profiler, XRF), layered pressed-record QC (100%
   optical inspection, per-cycle press telemetry, sampled automated audio