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/Private/Tactility/app/AppInstance.h

@@ -53,10 +53,10 @@ class AppInstance : public AppContext {
 #ifdef ESP_PLATFORM
             return createElfApp(manifest);
 #else
-            tt_crash("not supported");
+            check(false, "not supported");
 #endif
         } else {
-            tt_crash("not implemented");
+            check(false, "not implemented");
         }
     }