Start nixie clock project

Notes on the RetroModding IN-12 v2 clock (pinout, programming header,
plan for ESP_UniClock) and the maker's v2 schematic.

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

.gitignore

@@ -0,0 +1,23 @@
+# PlatformIO
+.pio/
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json
+.vscode/ipch
+
+# Flash dumps contain the stored WiFi password: keep them out of git
+firmware/stock/*.bin
+
+# Local credentials
+secrets.h
+
+# Claude Code local settings
+.claude/settings.local.json
+
+# OS files
+Thumbs.db
+desktop.ini
+.DS_Store
+
+# Editor temp / backup files
+*.swp