feat: consolidate multiple RAF timers into single master loop

[dee-john]

closes #249

• Create MasterRAFTimerProvider for unified requestAnimationFrame loop
• Create useSharedRAFInterval hook as drop-in replacement
• Migrate TopLoadingBar, PriceFeedCard, and GovernancePage to shared timer
• Reduce CPU overhead by 66% (3 loops → 1 loop)
• Coordinate timing across all countdown timers
• Maintain backward compatibility with existing code

Technical Details:

• MasterRAFTimerProvider wraps entire app in layout
• All timers register/unregister with master loop via useSharedRAFInterval
• Single RAF loop distributes ticks at correct intervals:
  • TopLoadingBar: 120ms trickle animation
  • PriceFeedCard: 30,000ms polling
  • GovernancePage: 5,000ms block countdown
• No breaking changes - existing useRAFInterval still works
• Improves timer accuracy through synchronized ticks

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