Optical QC: EtherCAT control plan with geizhals.de prices

User, 19 Oct 2026: plan the current EtherCAT setup, keep the 100 W servo,
check prices on geizhals.de.

- New docs/equipment/inline-qc-control-plan.md: decisions, bus layout
  (drives at the end of the line because the A6-200EC takes control
  power from the main supply), I/O list for EL1809/EL2809/EL3152/EL5101
  and the drive touch probe, PDO and DC notes from the A6-EC manual,
  geizhals.de price table (EUR 1,891.60 to 2,104.39 + USD 246.58 for the
  servo kits, THB 80k to 88k), NixOS/EtherCrab software, safety circuit
  (PNOZ s3, two contactors, dump valve), bench test with pass marks
  (parts about THB 64k, all reused), build order, spares, open points.
- EL3102 replaced by EL3152: the optoNCDT 1420 output is 4 to 20 mA.
- Spindle encoder index goes to an EL5101 instead of the drive touch
  probe; encoder 2,000 to 2,500 pulses.
- BOM: control lines split per part with geizhals.de prices (+30% high
  end for shipping and Thai duty/VAT, estimate); total USD 16,912 to
  33,061 (THB 0.56M to 1.09M). Doc, render caption and fleet calculator
  text now say USD 17k to 33k.
- README links the plan.

docs/equipment/inline-qc-station/annotate_render.py

@@ -14,7 +14,7 @@ TITLE = "Inline optical QC station"
 SUBTITLE = ("Every record checked on both faces in one turn: surface, label, warp and centring. "
             "Failed records leave the line automatically.")
 FOOTER = ("CNX Vinyl, concept model (FreeCAD); bought parts drawn as outlines. 1.9 × 0.65 × 1.5 m, "
-          "front panels and lid removed for the view. Hardware about USD 16k to 33k per station (estimate).")
+          "front panels and lid removed for the view. Hardware about USD 17k to 33k per station (estimate).")
 NAVY, GREY, LINE = (18, 53, 91), (85, 95, 105), (60, 74, 90)