feat: redesign all 5 tab icons with consistent style (五维×五行)

All icons now use consistent 81x81px size, uniform line weight,
and element-themed colors:
- 身(土): circle, orange #FF8C42
- 智(金): diamond, indigo #6366F1
- 富(水): water drop, amber #F59E0B
- 行(木): arrow up, emerald #10B981
- 心(火): heart, pink #FF6B9D

Normal = gray #999, Active = element color