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/Check.h

@@ -0,0 +1,32 @@
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <Tactility/Log.h>
+
+__attribute__((noreturn)) extern void __crash(void);
+
+#define CHECK_GET_MACRO(_1, _2, NAME, ...) NAME
+#define check(...) CHECK_GET_MACRO(__VA_ARGS__, CHECK_MSG, CHECK_NO_MSG)(__VA_ARGS__)
+
+#define CHECK_NO_MSG(condition) \
+    do { \
+        if (!(condition)) { \
+            LOG_E("Error", "Check failed: %s at %s:%d", #condition, __FILE__, __LINE__); \
+            __crash(); \
+        } \
+    } while (0)
+
+#define CHECK_MSG(condition, message) \
+    do { \
+        if (!(condition)) { \
+            LOG_E("Error", "Check failed: %s at %s:%d", message, __FILE__, __LINE__); \
+            __crash(); \
+        } \
+    } while (0)
+
+#ifdef __cplusplus
+}
+#endif