Challenges and small fixes update

✨ New

• Kaboom Challenge is now available — a brand new challenge mode to test your skills!
• Challenges now unlock in a queue, so multiple unlocks feel smooth and orderly.

⚡ Improved

• Challenge balance has been adjusted for a better experience.
• The AK tooltip has been updated with clearer information.

🐛 Fixed

• The HUD is now properly visible during PvP matches.
• Unit purchase button now correctly shows when you don't have enough gold to buy a unit.
• Fixed issues with hats and shop displays not loading correctly.