Butterfly EDFA Rack bridge: seed + EDFA over WiFi/MQTT to Home Assistant

ESP32 firmware bridging the 1550 nm MOPA (Koheron CTL200 seed + Agiltron
M511 two-stage EDFA) to MQTT/HA as a single device. Telemetry and control
for both instruments verified end-to-end: MQTT command -> seed lasing ->
booster ramp to 27 dBm (~515 mW) at the documented 2500 mA operating point.

- PlatformIO/Arduino project, project-local venv, Makefile upload flow
- Koheron ASCII driver on UART2; Agiltron binary 0x55AA driver on UART1
- HA discovery (sensors, binary_sensors, switches, numbers); LWT availability
- Static IP, firmware current clamps on seed and booster pump

Makefile

@@ -0,0 +1,41 @@
+# Koheron CTL200 -> WiFi/MQTT bridge on ESP32.
+#
+# All commands run PlatformIO from the project-local venv, so you never need
+# `pio` on your PATH. Just `make`, `make upload`, `make monitor`.
+
+VENV    := .venv
+PIO     := $(VENV)/bin/pio
+PORT    ?= /dev/ttyUSB0
+ENV     := esp32dev
+
+.PHONY: help build upload monitor flash clean detect erase venv
+
+help:                ## Show this help
+	@grep -E '^[a-zA-Z_-]+:.*?## .*$$' $(MAKEFILE_LIST) \
+	  | awk 'BEGIN{FS=":.*?## "}{printf "  \033[36m%-10s\033[0m %s\n", $$1, $$2}'
+
+build: $(PIO)        ## Compile firmware
+	$(PIO) run -e $(ENV)
+
+upload: $(PIO)       ## Compile + flash to the ESP32
+	$(PIO) run -e $(ENV) -t upload --upload-port $(PORT)
+
+monitor: $(PIO)      ## Open serial monitor (Ctrl-C to exit)
+	$(PIO) device monitor --port $(PORT) -b 115200
+
+flash: upload monitor ## Upload then immediately open the monitor
+
+detect: $(PIO)       ## Identify the chip on $(PORT)
+	$(VENV)/bin/python -m esptool --port $(PORT) chip_id
+
+erase: $(PIO)        ## Erase entire flash (factory reset)
+	$(VENV)/bin/python -m esptool --port $(PORT) erase_flash
+
+clean: $(PIO)        ## Remove build artifacts
+	$(PIO) run -e $(ENV) -t clean
+
+# Recreate the venv if it is missing (e.g. fresh checkout).
+venv $(PIO):
+	python3 -m venv $(VENV)
+	$(VENV)/bin/pip install --upgrade pip
+	$(VENV)/bin/pip install platformio esptool