fix(market): simplify watchlist empty state layout (OK-52427)

[limichange]

Summary

• Remove title and description text from watchlist empty state
• Simplify platform-specific positioning logic (remove absolute positioning)
• Unify maxSize to 8 for recommended tokens across all platforms

Changes Detail

• MarketRecommendList.tsx: Removed window height detection and conditional title/description rendering, simplified layout structure
• MobileMarketWatchlistFlatList.tsx: Removed platform-specific absolute positioning (iOS/Android bottom values), unified to simple paddingTop layout

Risk Assessment

• Risk Level: Low
• Affected Platforms: Mobile (iOS/Android), Extension
• Risk Areas: Visual layout change only, no logic changes

Test plan

• Verify watchlist empty state displays correctly on iOS
• Verify watchlist empty state displays correctly on Android
• Verify recommended tokens list shows 8 items on all platforms
• Verify layout is properly centered without absolute positioning

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[revan-zhang]

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 3 additional findings.