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.

Tactility/Source/kernel/SystemEvents.cpp

@@ -4,6 +4,7 @@
 #include <Tactility/Logger.h>
 #include <Tactility/Mutex.h>
 
+#include <Tactility/CoreDefines.h>
 #include <list>
 
 namespace tt::kernel {
@@ -53,7 +54,7 @@ static const char* getEventName(SystemEvent event) {
             return TT_STRINGIFY(Time);
     }
 
-    tt_crash(); // Missing case above
+    check(false); // Missing case above
 }
 
 void publishSystemEvent(SystemEvent event) {
@@ -83,7 +84,7 @@ SystemEventSubscription subscribeSystemEvent(SystemEvent event, OnSystemEvent ha
         mutex.unlock();
         return id;
     } else {
-        tt_crash();
+        check(false);
     }
 }