Initial commit: plasma DMD driver project

- Design docs: 12 V DC power supply, safety and bring-up, ESP32 interface, BOM
- PSU schematic (schemdraw) and KiCad 10 carrier-board project with HV net classes
- ESP32 PlatformIO firmware skeleton with HV watchdog toggle
- Reference schematic of the Stern 520-5138-00 display PSU

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,19 @@
+# PlatformIO
+firmware/.pio/
+firmware/.vscode/
+
+# KiCad backups, caches and local state
+*-backups/
+*.kicad_prl
+fp-info-cache
+*.lck
+\#auto_saved_files#
+_autosave-*
+*.bak
+
+# Python
+__pycache__/
+
+# KiCad generated reports
+hardware/kicad/erc.rpt
+*.net