Add find-me LED locate on master and slaves via ESP-NOW.

UART FIND_ME (client_id 0 = local ring, >0 = unicast), ESPNOW_FIND_ME payload, CLI/dashboard buttons per slave.

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

main/proto/uart_messages.proto

@@ -20,6 +20,7 @@ enum MessageType {
   OTA_STATUS = 19;
   OTA_START_ESPNOW = 20;
   OTA_SLAVE_PROGRESS = 21;
+  FIND_ME = 22;
 }
 
 message UartMessage {
@@ -42,6 +43,8 @@ message UartMessage {
     OtaSlaveProgressResponse ota_slave_progress_response = 16;
     LedRingProgressRequest led_ring_progress_request = 17;
     LedRingProgressResponse led_ring_progress_response = 18;
+    EspNowFindMeRequest espnow_find_me_request = 19;
+    EspNowFindMeResponse espnow_find_me_response = 20;
   }
 }
 
@@ -110,8 +113,8 @@ message EspNowUnicastTestResponse {
   uint32 seq = 2;
 }
 
-// Host → device: LED ring display (progress bar, digit, clear, or blink).
-// mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10), 3=blink full ring.
+// Host → device: LED ring display (progress bar, digit, clear, blink, or find-me).
+// mode: 0=clear, 1=progress (0–100 %), 2=digit (0–10), 3=blink full ring, 4=find-me (R/G/B ×3 @ full brightness).
 message LedRingProgressRequest {
   uint32 mode = 1;
   /** 0–100: fraction of ring LEDs to light (mode=progress) */
@@ -136,6 +139,16 @@ message LedRingProgressResponse {
   uint32 digit = 4;
 }
 
+/** Host → master: find-me on local ring (client_id=0) or ESP-NOW unicast to one slave. */
+message EspNowFindMeRequest {
+  uint32 client_id = 1;
+}
+
+message EspNowFindMeResponse {
+  bool success = 1;
+  uint32 client_id = 2;
+}
+
 // Host → device: begin UART OTA (erase inactive OTA slot; device replies OTA_STATUS).
 message OtaStartPayload {
   uint32 total_size = 1;