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/gpio.c

@@ -0,0 +1,77 @@
+/* USER CODE BEGIN Header */
+/**
+  ******************************************************************************
+  * @file    gpio.c
+  * @brief   This file provides code for the configuration
+  *          of all used GPIO pins.
+  ******************************************************************************
+  * @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 "gpio.h"
+
+/* USER CODE BEGIN 0 */
+
+/* USER CODE END 0 */
+
+/*----------------------------------------------------------------------------*/
+/* Configure GPIO                                                             */
+/*----------------------------------------------------------------------------*/
+/* USER CODE BEGIN 1 */
+
+/* USER CODE END 1 */
+
+/** Configure pins as
+        * Analog
+        * Input
+        * Output
+        * EVENT_OUT
+        * EXTI
+*/
+void MX_GPIO_Init(void)
+{
+
+  GPIO_InitTypeDef GPIO_InitStruct = {0};
+
+  /* GPIO Ports Clock Enable */
+  __HAL_RCC_GPIOC_CLK_ENABLE();
+  __HAL_RCC_GPIOD_CLK_ENABLE();
+  __HAL_RCC_GPIOA_CLK_ENABLE();
+  __HAL_RCC_GPIOB_CLK_ENABLE();
+
+  /*Configure GPIO pin Output Level */
+  HAL_GPIO_WritePin(GPIOC, GPIO_PIN_13, GPIO_PIN_RESET);
+
+  /*Configure GPIO pin : PC13 */
+  GPIO_InitStruct.Pin = GPIO_PIN_13;
+  GPIO_InitStruct.Mode = GPIO_MODE_OUTPUT_PP;
+  GPIO_InitStruct.Pull = GPIO_NOPULL;
+  GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
+  HAL_GPIO_Init(GPIOC, &GPIO_InitStruct);
+
+  /*Configure GPIO pin : PB7 */
+  GPIO_InitStruct.Pin = GPIO_PIN_7;
+  GPIO_InitStruct.Mode = GPIO_MODE_IT_RISING;
+  GPIO_InitStruct.Pull = GPIO_PULLDOWN;
+  HAL_GPIO_Init(GPIOB, &GPIO_InitStruct);
+
+  /* EXTI interrupt init*/
+  HAL_NVIC_SetPriority(EXTI9_5_IRQn, 0, 0);
+  HAL_NVIC_EnableIRQ(EXTI9_5_IRQn);
+
+}
+
+/* USER CODE BEGIN 2 */
+
+/* USER CODE END 2 */