Disable minimap rotation by default and fix settings checkbox

Changed default value from true to false in three places:
- Minimap class (rotateWithCamera member)
- GameScreen settings (minimapRotate_ and pendingMinimapRotate)
- Restore Interface Defaults button

The minimap will now remain fixed/north-up by default, and the settings
checkbox properly controls the rotation behavior.

include/rendering/minimap.hpp

@@ -78,7 +78,7 @@ private:
     int mapSize = 200;
     float viewRadius = 400.0f;  // world units visible in minimap radius
     bool enabled = true;
-    bool rotateWithCamera = true;
+    bool rotateWithCamera = false;
 
     // Throttling
     float updateIntervalSec = 0.25f;

include/ui/game_screen.hpp

@@ -70,11 +70,11 @@ private:
     float pendingMouseSensitivity = 0.2f;
     bool pendingInvertMouse = false;
     int pendingUiOpacity = 65;
-    bool pendingMinimapRotate = true;
+    bool pendingMinimapRotate = false;
 
     // UI element transparency (0.0 = fully transparent, 1.0 = fully opaque)
     float uiOpacity_ = 0.65f;
-    bool minimapRotate_ = true;
+    bool minimapRotate_ = false;
 
     /**
      * Render player info window