feat: add CoinIcon component for displaying cryptocurrency icons

feat: implement TradeModal for buying and selling coins with validation and transaction handling

feat: create server-side trade API for executing buy/sell transactions and updating user balances

feat: add transactions API to fetch user transaction history

feat: implement portfolio page to display user's holdings and recent transactions

website/src/lib/stores/user-data.ts

@@ -10,6 +10,8 @@ export type User = {
     isBanned: boolean;
     banReason: string | null;
     avatarUrl: string | null;
+
+    baseCurrencyBalance: number;
     bio: string;
 } | null;