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/components/self/CoinIcon.svelte

@@ -0,0 +1,33 @@
+<script lang="ts">
+	import { getPublicUrl } from '$lib/utils';
+
+	let {
+		icon,
+		symbol,
+		name = symbol,
+		size = 6,
+		class: className = ''
+	} = $props<{
+		icon?: string | null;
+		symbol: string;
+		name?: string;
+		size?: number;
+		class?: string;
+	}>();
+
+	let sizeClass = $derived(`h-${size} w-${size}`);
+</script>
+
+{#if icon}
+	<img
+		src={getPublicUrl(icon)}
+		alt={name}
+		class="{sizeClass} rounded-full object-cover {className}"
+	/>
+{:else}
+	<div
+		class="{sizeClass} bg-primary flex items-center justify-center overflow-hidden rounded-full {className}"
+	>
+		<span class="text-xs font-bold text-white">{symbol.slice(0, 2)}</span>
+	</div>
+{/if}