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/WifiMock.cpp

@@ -76,7 +76,7 @@ void setScanRecords(uint16_t records) {
 }
 
 std::vector<ApRecord> getScanResults() {
-    tt_check(wifi);
+    check(wifi);
 
     std::vector<ApRecord> records;
     records.push_back((ApRecord) {
@@ -145,14 +145,14 @@ class WifiService final : public Service {
 
 public:
 
-    bool onStart(TT_UNUSED ServiceContext& service) override {
-        tt_check(wifi == nullptr);
+    bool onStart(ServiceContext& service) override {
+        check(wifi == nullptr);
         wifi = new Wifi();
         return true;
     }
 
-    void onStop(TT_UNUSED ServiceContext& service) override {
-        tt_check(wifi != nullptr);
+    void onStop(ServiceContext& service) override {
+        check(wifi != nullptr);
         delete wifi;
         wifi = nullptr;
     }