Add USART2 support and modify system clock configuration

- Implemented USART2 initialization and interrupt handling.
- Added a function to send data to the server via USART2.
- Updated the main application to utilize USART2 for communication.
- Changed system clock configuration to use HSE and PLL for higher frequency.
- Adjusted SPI1 baud rate prescaler for improved performance.
- Enhanced LED control logic based on RFID card detection.
- Updated project configuration to reflect new USART2 settings.

Core/Inc/usart.h

@@ -34,11 +34,14 @@ extern "C" {
 
 extern UART_HandleTypeDef huart1;
 
+extern UART_HandleTypeDef huart2;
+
 /* USER CODE BEGIN Private defines */
 
 /* USER CODE END Private defines */
 
 void MX_USART1_UART_Init(void);
+void MX_USART2_UART_Init(void);
 
 /* USER CODE BEGIN Prototypes */