Added a Campaign Mode

1. Main Menu Restructured

• Start Game: Directly launches Campaign Mode

• Select Mode: Other game modes moved to this secondary menu

2. Settings

• Added Frame Rate Limit option

3. Campaign Mode (30 Waves + Endless Challenge)

• Genre: Top-down particle bullet-hell shooter + Roguelike card upgrade

• Controls: WASD to move core, Shift to sprint, mouse to aim, LMB to attract particles, ESC to pause