Butterfly EDFA Rack: Home Assistant config and dashboard

Fresh repo holding only the Butterfly-rack HA side (the firmware and BOM
live in koheron-esp32-bridge). Contents, pulled from the live HA host:

- configuration.butterfly.yaml: dBm->mW template sensors + the YAML
  dashboard registration, to merge into /config/configuration.yaml
- scripts.butterfly.yaml: the butterfly_edfa_shutdown emergency-off script
- ui-lovelace-butterfly.yaml: the dashboard
- deploy.sh: scp the dashboard, check_config, restart HA
- .gitignore guards against committing the HA DB, logs and secrets

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,13 @@
+# This repo holds only the Butterfly-rack HA config, not a full HA checkout.
+# Guard against accidentally committing runtime/DB/secret artefacts if someone
+# copies files in from a live /config.
+secrets.yaml
+home-assistant_v2.db*
+*.log
+*.log.*
+.storage/
+.cloud/
+__pycache__/
+*.pyc
+*.bak-*
+*~