feat(network): add device serial number to web UI (#2506)

src/network/CrossPointWebServer.cpp

@@ -6,9 +6,12 @@
 #include <HalStorage.h>
 #include <Logging.h>
 #include <WiFi.h>
+#include <esp_efuse.h>
+#include <esp_efuse_table.h>
 #include <esp_task_wdt.h>
 
 #include <algorithm>
+#include <cctype>
 
 #include "CrossPointSettings.h"
 #include "FontInstaller.h"
@@ -368,9 +371,27 @@ void CrossPointWebServer::handleStatus() const {
   doc["uptime"] = millis() / 1000;
   doc["device"] = gpio.deviceIsX3() ? "X3" : "X4";
 
-  String json;
-  serializeJson(doc, json);
-  server->send(200, "application/json", json);
+  char snBuf[33] = {0};
+  bool valid = false;
+  if (esp_efuse_read_field_blob(ESP_EFUSE_USER_DATA, snBuf, 256) == ESP_OK) {
+    valid = snBuf[0] != '\0' && snBuf[0] != (char)0xFF;
+    for (int i = 0; i < 32 && snBuf[i] != '\0'; i++) {
+      if (!std::isprint(static_cast<unsigned char>(snBuf[i]))) {
+        valid = false;
+        break;
+      }
+    }
+  }
+
+  if (valid) {
+    doc["serial"] = snBuf;
+  } else {
+    doc["serial"] = "Not found";
+  }
+
+  String response;
+  serializeJson(doc, response);
+  server->send(200, "application/json", response);
 }
 
 void CrossPointWebServer::scanFiles(const char* path, const std::function<void(FileInfo)>& callback) const {