Update token logos in mobile wallet to match web version

Changed token logos to match web interface:
- HEZ: 💎 → 🟡 (yellow circle)
- PEZ: 🪙 → 🟣 (purple circle)
- USDT: 💵 (unchanged)

This ensures consistent branding across web and mobile platforms.

mobile/src/screens/WalletScreen.tsx

@@ -65,7 +65,7 @@ const WalletScreen: React.FC = () => {
       balance: balances.HEZ,
       value: '$0.00',
       change: '+0.00%',
-      logo: '💎',
+      logo: '🟡',
       isLive: true,
     },
     {
@@ -74,7 +74,7 @@ const WalletScreen: React.FC = () => {
       balance: balances.PEZ,
       value: '$0.00',
       change: '+0.00%',
-      logo: '🪙',
+      logo: '🟣',
       isLive: true,
     },
     {