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/boot.py

@@ -0,0 +1,38 @@
+import network
+import time
+import json
+
+
+def load_config():
+    try:
+        with open('config.json') as f:
+            return json.load(f)
+    except OSError:
+        print('[boot] config.json not found, using defaults')
+        return {
+            'ssid': 'MyWiFi', 'password': 'secret',
+            'led_count': 300, 'strip_type': 'sk6812',
+            'led_pin': 5, 'spi_id': 1, 'udp_port': 21324
+        }
+
+
+def connect_wifi(ssid, password, timeout=15):
+    wlan = network.WLAN(network.STA_IF)
+    wlan.active(True)
+    if wlan.isconnected():
+        print('[boot] Already connected:', wlan.ifconfig()[0])
+        return wlan
+    print('[boot] Connecting to', ssid, '...')
+    wlan.connect(ssid, password)
+    start = time.time()
+    while not wlan.isconnected():
+        if time.time() - start > timeout:
+            print('[boot] WiFi timeout after', timeout, 'seconds')
+            return wlan
+        time.sleep(0.5)
+    print('[boot] Connected:', wlan.ifconfig()[0])
+    return wlan
+
+
+config = load_config()
+wlan = connect_wifi(config['ssid'], config['password'])