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/Pole.h

@@ -3,22 +3,25 @@
 #define POLE_H
 
 #include "Light.h"
+#include "Observer.h"
 #include "Pelican.h"
 
-class Pole {
+class Pole : public Observer {
   public:
-    Pole(int x, int y);
+    Pole(int x, int y, Pelican&);
     ~Pole();
 
     void setTrafficLights(Pelican::PelicanState state);
     void setWaitLight(bool pressed);
 
+    void update();
+
   private:
     enum LightName { RED_LIGHT, YELLOW_LIGHT, GREEN_LIGHT, GREEN_MAN, RED_MAN };
 
     Light *lights[RED_MAN + 1];
-
     Light *waitLight;
+    Pelican& pelican;
 };
 
 #endif