Add Northcott's Game interactive

Implemented Northcott's Game as an interactive within the games theme.
- Added game logic, board size selection, and misere mode toggle.
- Implemented two-player mode with visual turn indicators.

src/components/GamesGallery.tsx

@@ -5,6 +5,7 @@ import { Badge } from '@/components/ui/badge';
 import { Search } from 'lucide-react';
 import Layout from '@/components/Layout';
 import GameOfSim from '@/components/GameOfSim';
+import NorthcottsGame from '@/components/NorthcottsGame';
 
 interface Game {
   id: string;
@@ -21,6 +22,13 @@ const games: Game[] = [
     description: 'A strategic two-player game where you take turns coloring edges between vertices, trying to avoid creating a triangle of your own color.',
     tags: ['strategy', 'graph-theory', 'two-player', 'logic', 'game-theory'],
     component: GameOfSim
+  },
+  {
+    id: 'northcotts-game',
+    title: "Northcott's Game",
+    description: 'A classic strategy game played on a grid where players move pieces horizontally toward each other, trying to be the last one able to move.',
+    tags: ['strategy', 'two-player', 'grid-game', 'logic', 'movement'],
+    component: NorthcottsGame
   }
 ];