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/stm32f1xx_it.h

@@ -57,6 +57,7 @@ void PendSV_Handler(void);
 void SysTick_Handler(void);
 void I2C1_EV_IRQHandler(void);
 void USART1_IRQHandler(void);
+void USART2_IRQHandler(void);
 /* USER CODE BEGIN EFP */
 
 /* USER CODE END EFP */