refactor(net): unique_ptr for connection-lifecycle objects (#11459)

- WiFiServerAPI/ethServerAPI apiPort and ethApiServer's listener are
  create/destroy cycles that repeat across WiFi teardown and W5500
  chip resets; the manual delete+null bookkeeping becomes reset().
  (ethTlsApiServer's listener is left for a follow-up: that file is
  already touched by the partial-init fix PR and converting it here
  would conflict.)

- ContentHandler::handleFormUpload held its body parser raw with
  delete on four separate exit paths of a per-request handler; any
  future early return was a silent leak. unique_ptr removes all four.

- The portduino ch341Hal global becomes unique_ptr. The LoRa-error
  recovery loop's delete/null/new sequence was correct only by
  hand-preserved ordering; it becomes reset()/make_unique. RadioLibHAL
  keeps a non-owning raw pointer, as before.

No behavior change.

src/main.cpp

@@ -1498,14 +1498,13 @@ void loop()
         LOG_ERROR("LoRa error detected, recovering");
         router->addInterface(nullptr);
         if (portduino_config.lora_spi_dev == "ch341") {
-            if (ch341Hal != nullptr) {
-                delete ch341Hal;
-                ch341Hal = nullptr;
+            if (ch341Hal) {
+                ch341Hal.reset();
                 sleep(3);
             }
             try {
-                ch341Hal = new Ch341Hal(0, portduino_config.lora_usb_serial_num, portduino_config.lora_usb_vid,
-                                        portduino_config.lora_usb_pid);
+                ch341Hal = std::make_unique<Ch341Hal>(0, portduino_config.lora_usb_serial_num, portduino_config.lora_usb_vid,
+                                                      portduino_config.lora_usb_pid);
             } catch (std::exception &e) {
                 std::cerr << e.what() << std::endl;
                 std::cerr << "Could not initialize CH341 device!" << std::endl;