feat: implement ECS architecture with game entity management

- Introduced a new Entity-Component-System (ECS) architecture for the game.
- Created foundational components such as Transform, Velocity, Health, and Collidable.
- Developed systems for handling input, movement, collision detection, and rendering.
- Added game logic for player control, coin collection, and obstacle interactions.
- Implemented a performance monitor for real-time metrics display.
- Enhanced game initialization and entity creation processes.

This update significantly refactors the game structure, improving maintainability and scalability.

src/main.js

@@ -0,0 +1,18 @@
+import { Game } from './game/Game.js';
+
+// Start the game immediately (script is at end of body, DOM is ready)
+console.log('Starting 3D Coin Collector Game with ECS Architecture');
+console.log('Press "T" to toggle performance monitor (or shake device on mobile)');
+
+// Wait a tick to ensure everything is loaded
+setTimeout(() => {
+  try {
+    const game = new Game();
+    
+    // Make game accessible from console for debugging
+    window.game = game;
+  } catch (error) {
+    console.error('Game initialization failed:', error);
+  }
+}, 0);
+