feat(07-01): add firmware scaffold — boot.py, config.json, led_driver.py, protocol tests

- firmware/boot.py: WiFi connection on startup (MicroPython boot sequence)
- firmware/config.json: default device config with all 9 fields (ssid, password, led_count, strip_type, led_pin, spi_id, spi_clk_pin, spi_dat_pin, udp_port)
- firmware/led_driver.py: NeoPixelStrip (SK6812 RGBW) and WS2801Strip (RGB SPI) with unified interface (write_rgb, write_rgbw, fill, clear)
- tests/test_firmware_protocol.py: 21 host-side tests for round-trip protocol parsing (DRGB, DRGBW, DNRGB, animation_cmd)

firmware/config.json

@@ -0,0 +1,11 @@
+{
+  "ssid": "MyWiFi",
+  "password": "secret",
+  "led_count": 300,
+  "strip_type": "sk6812",
+  "led_pin": 5,
+  "spi_id": 1,
+  "spi_clk_pin": 18,
+  "spi_dat_pin": 23,
+  "udp_port": 21324
+}