Add unlockable cosmetic rewards tied to streaks and milestones

[NickTheDevOpsGuy]

Summary

Phuzzle has good stats and streak mechanics, but it needs more delightful long-term rewards players can show off.

Reward ideas

• Theme variants
• Tray skins
• Piece glow styles
• Badge frames
• Seasonal cosmetic unlocks

Scope

• Define a first small reward set.
• Hook unlocks into existing stats, streak, or achievement events.
• Add a lightweight place for players to see what they have earned.

Acceptance Criteria

• Players can unlock at least one visible cosmetic reward through normal play.
• Reward unlocks are persisted and shown in the UI.
• The reward system feels celebratory but not noisy.
• Locked versus unlocked states are easy to understand.

Bucket

Mid-size feature