Various improvements (#461)

* **New Features**
  * Time and delay utilities added (ticks, ms, µs); SD card now uses an expansion-header CS pin; HTTP downloads warn when run on the GUI task and yield to avoid blocking.

* **Bug Fixes / Reliability**
  * Many hard-crash paths converted to guarded checks to reduce abrupt termination and improve stability.

* **Tests**
  * Unit tests added to validate time and delay accuracy.

* **Chores**
  * License header and build/macro updates.

TactilityKernel/Include/Tactility/concurrent/RecursiveMutex.h

@@ -3,7 +3,7 @@
 #pragma once
 
 #include <stdbool.h>
-#include <assert.h>
+#include <Tactility/Check.h>
 #include <Tactility/FreeRTOS/semphr.h>
 
 #ifdef __cplusplus
@@ -19,14 +19,14 @@ inline static void recursive_mutex_construct(struct RecursiveMutex* mutex) {
 }
 
 inline static void recursive_mutex_destruct(struct RecursiveMutex* mutex) {
-    assert(mutex->handle != NULL);
-    vPortAssertIfInISR();
+    check(mutex->handle != NULL);
+    check(xPortInIsrContext() != pdTRUE);
     vSemaphoreDelete(mutex->handle);
     mutex->handle = NULL;
 }
 
 inline static void recursive_mutex_lock(struct RecursiveMutex* mutex) {
-    assert(xPortInIsrContext() != pdTRUE);
+    check(xPortInIsrContext() != pdTRUE);
     xSemaphoreTakeRecursive(mutex->handle, portMAX_DELAY);
 }
 
@@ -39,17 +39,17 @@ inline static bool recursive_mutex_is_locked(struct RecursiveMutex* mutex) {
 }
 
 inline static bool recursive_mutex_try_lock(struct RecursiveMutex* mutex) {
-    assert(xPortInIsrContext() != pdTRUE);
+    check(xPortInIsrContext() != pdTRUE);
     return xSemaphoreTakeRecursive(mutex->handle, 0) == pdTRUE;
 }
 
 inline static bool recursive_mutex_try_lock_timed(struct RecursiveMutex* mutex, TickType_t timeout) {
-    assert(xPortInIsrContext() != pdTRUE);
+    check(xPortInIsrContext() != pdTRUE);
     return xSemaphoreTakeRecursive(mutex->handle, timeout) == pdTRUE;
 }
 
 inline static void recursive_mutex_unlock(struct RecursiveMutex* mutex) {
-    assert(xPortInIsrContext() != pdTRUE);
+    check(xPortInIsrContext() != pdTRUE);
     xSemaphoreGiveRecursive(mutex->handle);
 }