feat: implement Geant Material class, add object registration, and update PropertyWidget signal handling and read-only state

src/HEP/Geant/CMakeLists.txt

@@ -27,6 +27,8 @@ set(SOURCES
     Scene.cpp
     Solid.cpp
     EmitterPrimary.cpp
+    Matter.cpp
+    GeantRegistration.cpp
     DetectorConstruction.cpp
     PhysicsList.cpp
     ActionInitialization.cpp