Fix web OTA upload and isolate OTA sessions across firmware and goTool.

Split ESP-NOW into core/master/slave modules, block non-OTA UART traffic during updates, and hold the host serial port exclusively so dashboard polling cannot interleave with firmware uploads.

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

main/ota_session.c

@@ -0,0 +1,25 @@
+#include "ota_session.h"
+#include "ota_espnow.h"
+#include "ota_uart.h"
+#include "uart_messages.pb.h"
+
+bool ota_session_busy(void) {
+  return ota_uart_is_active() || ota_espnow_distribution_active();
+}
+
+bool ota_session_uart_cmd_allowed(uint16_t msg_id) {
+  if (!ota_session_busy()) {
+    return true;
+  }
+
+  switch ((alox_MessageType)msg_id) {
+  case alox_MessageType_OTA_START:
+  case alox_MessageType_OTA_PAYLOAD:
+  case alox_MessageType_OTA_END:
+  case alox_MessageType_OTA_START_ESPNOW:
+  case alox_MessageType_OTA_SLAVE_PROGRESS:
+    return true;
+  default:
+    return false;
+  }
+}