Add ESP32-S3 BLE-to-RS422 bridge firmware for Carryout G2

NimBLE-based Nordic UART Service (NUS) bridge on ESP32-S3-DevKitC-1.
Transparent passthrough: BLE client writes → UART1 TX → RS-422 → G2,
and G2 → RS-422 → UART1 RX → BLE notifications. USB serial serves as
debug monitor and fallback input.

Uses two MAX485 modules (one locked TX, one locked RX) with a SparkFun
BSS138 level converter for 3.3V/5V translation. Wiring schematic and
RJ-12 pinout documented in docs/ble-bridge-wiring.md.

firmware/ble-bridge/include/config.h

@@ -0,0 +1,39 @@
+#pragma once
+
+// --- GPIO Pin Assignments ---
+// UART1 to RS-422 module via 3.3V<->5V level shifter
+#define PIN_RS422_TX 17  // ESP32 TX -> level shifter -> MAX490 RXD
+#define PIN_RS422_RX 18  // MAX490 TXD -> level shifter -> ESP32 RX
+
+// Onboard RGB LED (WS2812, DevKitC-1 V1.1)
+#define PIN_LED 38
+
+// --- RS-422 UART (UART1) ---
+#define RS422_BAUD 115200
+#define RS422_CONFIG SERIAL_8N1
+
+// --- BLE Configuration ---
+#define BLE_DEVICE_NAME "Travler-G2"
+#define BLE_MTU 517
+// Max payload per NUS notification (must fit in ATT_MTU - 3)
+#define BLE_NOTIFY_MAX 240
+
+// Nordic UART Service UUIDs
+#define NUS_SERVICE_UUID "6E400001-B5A3-F393-E0A9-E50E24DCCA9E"
+#define NUS_RX_UUID      "6E400002-B5A3-F393-E0A9-E50E24DCCA9E"  // Client writes here
+#define NUS_TX_UUID      "6E400003-B5A3-F393-E0A9-E50E24DCCA9E"  // ESP32 notifies here
+
+// --- Timing ---
+// Inter-byte coalescing window: collect bytes arriving within this
+// gap into one BLE notification instead of sending byte-by-byte
+#define COALESCE_MS 3
+
+// LED refresh interval
+#define LED_UPDATE_MS 50
+
+// --- LED ---
+#define LED_BRIGHTNESS 30  // 0-255, keep low to avoid blinding in enclosure
+#define LED_COUNT 1
+
+// --- Buffers ---
+#define UART_RX_BUF_SIZE 512