fix(server): defer 0xFF OTA confirm to fix race condition

src/main.cpp

@@ -70,6 +70,7 @@ bool otaShaStarted = false;
 bool otaReady = false;
 bool otaEnded = false;
 bool otaConfirmed = false;
+bool otaEarlyConfirm = false;
 uint32_t otaEndedAt = 0;
 #define OTA_CONFIRM_TIMEOUT_MS 10000
 
@@ -191,6 +192,7 @@ static void otaReset() {
     otaReady = false;
     otaEnded = false;
     otaConfirmed = false;
+    otaEarlyConfirm = false;
     if (otaShaStarted) {
         mbedtls_sha256_free(&otaShaCtx);
         otaShaStarted = false;
@@ -296,7 +298,8 @@ class OtaCharacteristicCallbacks : public NimBLECharacteristicCallbacks {
             Serial.printf("OTA: 0xFF received — otaReady=%d, otaEnded=%d, otaConfirmed=%d, otaInProgress=%d\n",
                           otaReady, otaEnded, otaConfirmed, otaInProgress);
             if (!otaEnded) {
-                Serial.println("OTA: 0xFF IGNORED — otaEnded is false (esp_ota_end not yet called or failed)");
+                Serial.println("OTA: 0xFF arrived early (esp_ota_end not yet called), deferring");
+                otaEarlyConfirm = true;
                 return;
             }
             Serial.println("OTA: 0xFF confirm accepted, setting otaConfirmed=true");
@@ -550,6 +553,12 @@ void loop() {
                       otaReady, otaEnded, otaConfirmed, otaInProgress);
     }
 
+    if (otaEnded && otaEarlyConfirm) {
+        Serial.println("OTA: processing deferred 0xFF confirm");
+        otaConfirmed = true;
+        otaEarlyConfirm = false;
+    }
+
     if (otaEnded && !otaConfirmed && (millis() - otaEndedAt > OTA_CONFIRM_TIMEOUT_MS)) {
         Serial.printf("OTA: 0xFF confirm timeout (%lu ms) — discarding update, resuming normal operation\n",
                       millis() - otaEndedAt);