feat(bridge): add wifi/serial bridge runtime and UI

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/espnow-binary-protocol.md

@@ -20,6 +20,8 @@ All ESP-NOW datagrams and Pi↔bridge WebSocket frames use **binary only** (no J
 | `0x02` | `GROUPS` | Controller → driver |
 | `0x03` | `CMD` | Controller → driver |
 | `0x04` | `GROUP_CMD` | Controller → broadcast |
+| `0x05` | `PING_REQ` | Controller → broadcast |
+| `0x06` | `PING_RSP` | Driver → controller (unicast) |
 | `0x10` | `BRIDGE_CH` | Controller → broadcast |
 
 ### ANNOUNCE (`0x01`)
@@ -57,6 +59,24 @@ Bytes 2… are a **v2 binary envelope** (see `src/util/binary_envelope.py`): 5-b
 
 Drivers apply the nested envelope only if `group_id` is in their stored group list.
 
+### PING_REQ (`0x05`)
+
+Controller discovery ping (broadcast). Drivers reply with **PING_RSP** after a random delay (50–500 ms) to reduce ESP-NOW collisions.
+
+| Field | Type |
+|-------|------|
+| ping_id | u32 LE |
+
+### PING_RSP (`0x06`)
+
+Unicast to the bridge/controller peer that sent the request (ESP-NOW source MAC of the received **PING_REQ**).
+
+| Field | Type |
+|-------|------|
+| ping_id | u32 LE |
+| name_len | u8 |
+| name | UTF-8 |
+
 ### BRIDGE_CH (`0x10`)
 
 | Field | Type |