feat(cmat): implement Ex41 observer pattern

Refactor the Pelican crossing exercise to use the Observer
pattern: Pelican acts as Subject and each Pole observes it,
replacing direct calls through the owned Pole pointer.

Co-authored-by: Qwen 3.8 27B <qwen3.8_27b-q3_k_xl@lmstudio.local>

cmat/Ex41/main.cpp

@@ -1,13 +1,16 @@
 
 #include "Keyboard.h"
 #include "Pelican.h"
+#include "Pole.h"
 #include "TimerSet.h"
 
 #include <cctype> // provides toupper()
 
 int main() {
     Keyboard kbd;
-    Pelican thePelican(30, 0);
+    Pelican thePelican;
+    Pole pole1(20, 0, thePelican);
+    Pole pole2(40, 0, thePelican);
 
     char c = 0;