chore(outputs): regenerate STEP and PCBWay fabrication package

* firstpcb.step regenerated from current PCB (DRC-clean board with
  four M2 mounting holes). Two component 3D models (R_0805 and
  JST_XH_B4B-XH-A) fail to decompress under the Nix-packaged KiCad;
  affected components are missing 3D shapes but board body and other
  models are present.
* pcbway_export/ contains gerbers (RS-274X Protel, 4.6 mm), separate
  PTH/NPTH Excellon drill files, drill maps, gbrjob, and a README
  with the stackup/spec.
* firstpcb_pcbway.zip is the upload-ready archive for PCBWay.
* .gitignore updated to drop KiCad autosaves and *.pre-drc-fix locals.

Constraint: PCBWay accepts gerbers with Protel extensions and Excellon
  drills, separate PTH/NPTH preferred
Directive: regenerate this package whenever the PCB changes -- the zip
  is a derived artifact; the source of truth is firstpcb.kicad_pcb

pcbway_export/firstpcb-Edge_Cuts.gm1

@@ -0,0 +1,23 @@
+G04 #@! TF.GenerationSoftware,KiCad,Pcbnew,10.0.0*
+G04 #@! TF.CreationDate,2026-05-15T16:38:12-04:00*
+G04 #@! TF.ProjectId,firstpcb,66697273-7470-4636-922e-6b696361645f,rev?*
+G04 #@! TF.SameCoordinates,Original*
+G04 #@! TF.FileFunction,Profile,NP*
+%FSLAX46Y46*%
+G04 Gerber Fmt 4.6, Leading zero omitted, Abs format (unit mm)*
+G04 Created by KiCad (PCBNEW 10.0.0) date 2026-05-15 16:38:12*
+%MOMM*%
+%LPD*%
+G01*
+G04 APERTURE LIST*
+G04 #@! TA.AperFunction,Profile*
+%ADD10C,0.050000*%
+G04 #@! TD*
+G04 APERTURE END LIST*
+D10*
+X60000000Y-40000000D02*
+X141000000Y-40000000D01*
+X141000000Y-100000000D01*
+X60000000Y-100000000D01*
+X60000000Y-40000000D01*
+M02*