- Replace 11 per-frequency build environments with 3 role-based targets
(production, debug, test) using shared [env] base section
- Move LoRa frequency and sender-ID config from build flags into config.h
so all variants build from the same source
- Add -fstack-protector-strong, -D_FORTIFY_SOURCE=2, -Wformat-security
- Add Unity test framework to lib_deps for pio test support
- Add __pycache__/ to .gitignore
