Fix bug: prevent redrawing of already drawn horizontal/vertical lines

Bug Description: Players are able to draw a horizontal or vertical line that has already been drawn, which causes inconsistencies in gameplay and scoring.

Expected Behavior: An IllegalStateException should be thrown if a player attempts to draw an existing line.

Steps Taken:

• Created unit tests that fail for this bug
• Pushed tests and tagged the commit as 'testsfail'
• Fixed the bug in drawHorizontal() and drawVertical() by checking existing lines
• Pushed passing tests and merged fix to main

Fixed in commit 3d9021c0