🎨 Palette: Add explicit empty state for Personal Best

[EiJackGH]

💡 What: Added an explicit empty state ("None yet! Set a record!") for the Personal Best section when the high score is zero.
🎯 Why: Previously, the section was simply hidden. Hiding UI elements for achievements when empty makes the system state unclear and hurts onboarding.
♿ Accessibility/UX: Provides an encouraging, explicit empty state that clarifies the system's tracking mechanism for new users.

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PR created automatically by Jules for task 1077829044956618824 started by @EiJackGH

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