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/service/wifi/Wifi.cpp

@@ -1,6 +1,7 @@
 #include <Tactility/service/wifi/Wifi.h>
 
 #include <Tactility/Check.h>
+#include <Tactility/CoreDefines.h>
 #include <Tactility/service/ServiceManifest.h>
 #include <Tactility/service/ServiceRegistration.h>
 
@@ -22,7 +23,7 @@ const char* radioStateToString(RadioState state) {
         case Off:
             return TT_STRINGIFY(Off);
     }
-    tt_crash("not implemented");
+    check(false, "not implemented");
 }
 
 extern const ServiceManifest manifest;