Add CAN communication and GPIO control functionality

- Created HAL configuration file for STM32F1xx (stm32f1xx_hal_conf.h).
- Added interrupt handler definitions in stm32f1xx_it.h.
- Implemented CAN initialization and configuration in can.c.
- Configured GPIO pins for output and external interrupts in gpio.c.
- Developed main application logic in main.c for toggling an LED and sending CAN messages.
- Implemented MSP initialization and de-initialization for CAN in stm32f1xx_hal_msp.c.
- Defined interrupt service routines in stm32f1xx_it.c for CAN and EXTI interrupts.
- Added README for project-specific libraries and PlatformIO configuration.
- Created platformio.ini for project build settings.
- Added stm32pio.ini for CubeMX integration with PlatformIO.
- Included README for testing directory to guide unit testing setup.

firmware/components/can_testing/canblinker/Src/stm32f1xx_hal_msp.c

@@ -0,0 +1,86 @@
+/* USER CODE BEGIN Header */
+/**
+  ******************************************************************************
+  * @file         stm32f1xx_hal_msp.c
+  * @brief        This file provides code for the MSP Initialization
+  *               and de-Initialization codes.
+  ******************************************************************************
+  * @attention
+  *
+  * Copyright (c) 2025 STMicroelectronics.
+  * All rights reserved.
+  *
+  * This software is licensed under terms that can be found in the LICENSE file
+  * in the root directory of this software component.
+  * If no LICENSE file comes with this software, it is provided AS-IS.
+  *
+  ******************************************************************************
+  */
+/* USER CODE END Header */
+
+/* Includes ------------------------------------------------------------------*/
+#include "main.h"
+/* USER CODE BEGIN Includes */
+
+/* USER CODE END Includes */
+
+/* Private typedef -----------------------------------------------------------*/
+/* USER CODE BEGIN TD */
+
+/* USER CODE END TD */
+
+/* Private define ------------------------------------------------------------*/
+/* USER CODE BEGIN Define */
+
+/* USER CODE END Define */
+
+/* Private macro -------------------------------------------------------------*/
+/* USER CODE BEGIN Macro */
+
+/* USER CODE END Macro */
+
+/* Private variables ---------------------------------------------------------*/
+/* USER CODE BEGIN PV */
+
+/* USER CODE END PV */
+
+/* Private function prototypes -----------------------------------------------*/
+/* USER CODE BEGIN PFP */
+
+/* USER CODE END PFP */
+
+/* External functions --------------------------------------------------------*/
+/* USER CODE BEGIN ExternalFunctions */
+
+/* USER CODE END ExternalFunctions */
+
+/* USER CODE BEGIN 0 */
+
+/* USER CODE END 0 */
+/**
+  * Initializes the Global MSP.
+  */
+void HAL_MspInit(void)
+{
+
+  /* USER CODE BEGIN MspInit 0 */
+
+  /* USER CODE END MspInit 0 */
+
+  __HAL_RCC_AFIO_CLK_ENABLE();
+  __HAL_RCC_PWR_CLK_ENABLE();
+
+  /* System interrupt init*/
+
+  /** NOJTAG: JTAG-DP Disabled and SW-DP Enabled
+  */
+  __HAL_AFIO_REMAP_SWJ_NOJTAG();
+
+  /* USER CODE BEGIN MspInit 1 */
+
+  /* USER CODE END MspInit 1 */
+}
+
+/* USER CODE BEGIN 1 */
+
+/* USER CODE END 1 */