[enhancement][monitoring]: Add a visual indicator for serial print operations using LED_BUILTIN.

- SerialPrinter: Set LED_BUILTIN HIGH before scheduling a print operation to indicate print activity.
- PrintHandler: Set LED_BUILTIN LOW after printing to signal completion of the print operation.

Signed-off-by: Goran Mišković <[email protected]>

Author: schkovich

src/PrintHandler.cpp

@@ -32,6 +32,7 @@ namespace e5 {
     void  PrintHandler::onWork() {
         if (!m_message->empty()) {
             Serial1.print(m_message->c_str());
+            digitalWrite(LED_BUILTIN, LOW);
         }
     }
 

src/SerialPrinter.cpp

@@ -10,14 +10,15 @@
 #include "ContextManager.hpp"
 #include "MessageBuffer.hpp"
 #include "PrintHandler.hpp"
-
+#include "pins_arduino.h"
 namespace e5 {
 
     // Constructor implementation
     SerialPrinter::SerialPrinter(const AsyncCtx &ctx) : m_ctx(ctx) {}
 
     // Print method implementation for std::string
     uint32_t SerialPrinter::print(std::unique_ptr<std::string> message) const {
+        digitalWrite(LED_BUILTIN, HIGH);
         PrintHandler::create(m_ctx, std::move(message));
         return PICO_OK; // Return success code
     }