feat: upgrade platform and support webdav (#1047)

## Summary
- Upgrade platform from espressif32 6.12.0 (Arduino Core 2.0.17) to
pioarduino 55.03.37 (Arduino Core 3.3.7, ESP-IDF 5.5.2)
- Add WebDAV Class 1 server (RFC 4918) - SD card can be mounted as a
network drive
- I also slightly fixed the SDK and also made a [pull request
](https://github.com/open-x4-epaper/community-sdk/pull/21)

First PR #1030 (was closed because the implementation was based on an
old version of the libraries)
Issue #439

---------

Co-authored-by: Dave Allie <dave@daveallie.com>

src/network/CrossPointWebServer.cpp

@@ -159,6 +159,12 @@ void CrossPointWebServer::begin() {
   server->onNotFound([this] { handleNotFound(); });
   LOG_DBG("WEB", "[MEM] Free heap after route setup: %d bytes", ESP.getFreeHeap());
 
+  // Collect WebDAV headers and register handler
+  const char* davHeaders[] = {"Depth", "Destination", "Overwrite", "If", "Lock-Token", "Timeout"};
+  server->collectHeaders(davHeaders, 6);
+  server->addHandler(&davHandler);
+  LOG_DBG("WEB", "WebDAV handler initialized");
+
   server->begin();
 
   // Start WebSocket server for fast binary uploads
@@ -502,7 +508,7 @@ void CrossPointWebServer::handleDownload() const {
   server->sendHeader("Content-Disposition", "attachment; filename=\"" + filename + "\"");
   server->send(200, contentType.c_str(), "");
 
-  WiFiClient client = server->client();
+  NetworkClient client = server->client();
   client.write(file);
   file.close();
 }