fix: ArduinoOTA init, reporter mutex, BLE lock scope, NVS type

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

firmware/src/main.cpp

@@ -1,6 +1,7 @@
 // firmware/src/main.cpp
 #include <Arduino.h>
 #include <WiFi.h>
+#include <ArduinoOTA.h>
 #include "config.h"
 #include "provisioning.h"
 #include "camera.h"
@@ -139,8 +140,17 @@ void setup() {
         while (true) delay(1000);
     }
 
+    reporter_init();
+
     ble_scanner_start();
 
+    // OTA update support
+    ArduinoOTA.setHostname(g_cfg.device_id.c_str());
+    ArduinoOTA.onStart([]() { ble_scanner_pause(); });
+    ArduinoOTA.onEnd([]()   { ble_scanner_resume(); ESP.restart(); });
+    ArduinoOTA.onError([](ota_error_t e) { ble_scanner_resume(); });
+    ArduinoOTA.begin();
+
     s_cv_mutex = xSemaphoreCreateMutex();
 
     xTaskCreatePinnedToCore(task_camera,   "cam",  4096, nullptr, 2, nullptr, 1);
@@ -148,6 +158,7 @@ void setup() {
 }
 
 void loop() {
+    ArduinoOTA.handle();
     check_factory_reset();
 
     if (WiFi.status() != WL_CONNECTED) {