Add RESTART command for master and slaves via ESP-NOW.

UART RESTART (client_id 0 = local reboot, >0 = unicast); dashboard and CLI hooks; delayed esp_restart after response.

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

main/proto/uart_messages.proto

@@ -21,6 +21,7 @@ enum MessageType {
   OTA_START_ESPNOW = 20;
   OTA_SLAVE_PROGRESS = 21;
   FIND_ME = 22;
+  RESTART = 23;
 }
 
 message UartMessage {
@@ -45,6 +46,8 @@ message UartMessage {
     LedRingProgressResponse led_ring_progress_response = 18;
     EspNowFindMeRequest espnow_find_me_request = 19;
     EspNowFindMeResponse espnow_find_me_response = 20;
+    RestartRequest restart_request = 21;
+    RestartResponse restart_response = 22;
   }
 }
 
@@ -149,6 +152,16 @@ message EspNowFindMeResponse {
   uint32 client_id = 2;
 }
 
+/** Host → master: restart local node (client_id=0) or ESP-NOW unicast to one slave. */
+message RestartRequest {
+  uint32 client_id = 1;
+}
+
+message RestartResponse {
+  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;