refactor: route OTA version check through HttpDownloader (#2076)

With both OtaUpdater and HttpDownloader on esp_http_client
(https://github.com/crosspoint-reader/crosspoint-reader/pull/2074,
https://github.com/crosspoint-reader/crosspoint-reader/pull/2075),
checkForUpdate no longer needs its own client and event handler to fetch
the release JSON. It streams the response straight into
ReleaseJsonParser through a new HttpDownloader::fetchUrl(url,
DataCallback) overload, dropping the duplicate esp_http_client setup,
the HTTP_EVENT_ON_DATA handler, and the totalBytesReceived file global.

DataCallback hands body chunks to a callback without buffering. The
naive alternative, collecting the ~32KB JSON into a std::string, aborts
under -fno-exceptions: the growing allocation collides with the TLS
session's heap mid-fetch and operator new calls abort().

The OTA install path stays on esp_https_ota (flash-write streaming),
which has no HttpDownloader equivalent.

HttpDownloader.h must precede the lwip (esp_http_client) headers in
OtaUpdater.cpp, or Arduino/SdFat macros collide with lwip.


Did you use AI tools to help write this code? partial

src/network/HttpDownloader.h

@@ -12,6 +12,9 @@
 class HttpDownloader {
  public:
   using ProgressCallback = std::function<void(size_t downloaded, size_t total)>;
+  // Called with each body chunk as it arrives; return false to abort. Lets a
+  // streaming parser consume the response without buffering the whole body.
+  using DataCallback = std::function<bool(const uint8_t* data, size_t len)>;
 
   enum DownloadError {
     OK = 0,
@@ -29,6 +32,12 @@ class HttpDownloader {
   static bool fetchUrl(const std::string& url, Stream& stream, const std::string& username = "",
                        const std::string& password = "");
 
+  /**
+   * Stream the response body to onData as it arrives, without buffering it.
+   */
+  static bool fetchUrl(const std::string& url, const DataCallback& onData, const std::string& username = "",
+                       const std::string& password = "");
+
   /**
    * Download a file to the SD card with optional credentials.
    */