Game bug fixes and content updates

1. Fixed multiple issues where players couldn't return to their original route.
2. Added save functionality - players no longer need to complete the game in one session, can continue from last save after returning to main menu or quitting.
3. Added safety checks to respawn points to prevent players from respawning in unsafe areas causing repeated deaths.
4. Fixed bug where characters would get stuck in terrain on the main interface.
5. Added some additional NPC characters to the game.
6. Fixed bug where the 'Unstick' function would cause save point confusion.
7. Added some hints and tips.
8. Added new items to make routes more diverse.
9. Removed multiple erroneous colliders to ensure smooth character movement.