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/esp_now_messages.proto

@@ -16,6 +16,7 @@ enum EspNowMessageType {
   ESPNOW_OTA_END = 8;
   ESPNOW_OTA_STATUS = 9;
   ESPNOW_FIND_ME = 10;
+  ESPNOW_RESTART = 11;
 }
 
 message EspNowUnicastTest {
@@ -28,6 +29,11 @@ message EspNowFindMe {
   uint32 client_id = 1;
 }
 
+/** Master → slave: reboot after short delay. */
+message EspNowRestart {
+  uint32 client_id = 1;
+}
+
 message EspNowDiscover {
   uint32 network = 1;
 }
@@ -80,5 +86,6 @@ message EspNowMessage {
     EspNowOtaEnd ota_end = 9;
     EspNowOtaStatus ota_status = 10;
     EspNowFindMe find_me = 11;
+    EspNowRestart restart = 12;
   }
 }