🎨 Palette: Add explicit empty state for high score

[EiJackGH]

💡 What

Added an explicit, encouraging empty state for the "Personal Best" score display when a user plays the game for the first time (i.e., when highscore == 0).

🎯 Why

Previously, if a user had no high score, the "Personal Best" line was completely omitted from the UI. Hiding UI elements dynamically can leave users wondering where that data lives or if the feature is broken. An explicit empty state ("None yet! Play to set one!") clarifies the system state, acts as a gentle call-to-action, and improves the onboarding experience for new players.

📸 Before/After

Before (New Player):

==========================
      SPEED CLICKER
==========================
Controls:
 [h] Toggle Hard Mode (10x Speed!)
...

After (New Player):

==========================
      SPEED CLICKER
==========================
 Personal Best: None yet! Play to set one!

Controls:
 [h] Toggle Hard Mode (10x Speed!)
...

♿ Accessibility

While primarily a usability and onboarding improvement, providing explicit textual states rather than relying on visual absence makes the application logic clearer and easier to parse for all users.

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PR created automatically by Jules for task 1008036951818451356 started by @EiJackGH

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