Initial backup of LTP-305G matrix clock setup on matrixpi

Captures everything needed to redeploy the two-display clock (hour on I2C
0x61, minute on I2C 0x63) on a fresh Pi:

- Both systemd units (matrix0x61.service, matrix0x63.service)
- Deployed Pimoroni script tree, including the local %I (12-hour) clock
  customization
- Vendored upstream sources (ltp305-python, breakout-garden) so restore is
  fully offline-capable
- Boot config snippet enabling I2C
- install.sh that wires it all back up idempotently
- Inventory doc cross-referencing every live-system path

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

vendor/ltp305-python/.gitignore

@@ -0,0 +1,20 @@
+build/
+_build/
+*.o
+*.so
+*.a
+*.py[cod]
+*.egg-info
+dist/
+__pycache__
+.DS_Store
+*.deb
+*.dsc
+*.build
+*.changes
+*.orig.*
+packaging/*tar.xz
+library/debian/
+.coverage
+.pytest_cache
+.tox