refactor: add leveling view layer

Create leveling.view.ts with UI logic extracted from leaderboard command:
- getLeaderboardEmbed() for leaderboard display (XP and Balance)
- getMedalEmoji() helper for ranking medals (🥇🥈🥉)
- formatLeaderEntry() helper for entry formatting with null safety

Updated leaderboard.ts to use view functions instead of inline formatting.

src/modules/leveling/leveling.view.ts

@@ -0,0 +1,48 @@
+import { EmbedBuilder } from "discord.js";
+
+/**
+ * User data for leaderboard display
+ */
+interface LeaderboardUser {
+    username: string;
+    level: number | null;
+    xp: bigint | null;
+    balance: bigint | null;
+}
+
+/**
+ * Returns the appropriate medal emoji for a ranking position
+ */
+function getMedalEmoji(index: number): string {
+    if (index === 0) return "🥇";
+    if (index === 1) return "🥈";
+    if (index === 2) return "🥉";
+    return `${index + 1}.`;
+}
+
+/**
+ * Formats a single leaderboard entry based on type
+ */
+function formatLeaderEntry(user: LeaderboardUser, index: number, type: 'xp' | 'balance'): string {
+    const medal = getMedalEmoji(index);
+    const value = type === 'xp'
+        ? `Lvl ${user.level ?? 1} (${user.xp ?? 0n} XP)`
+        : `${user.balance ?? 0n} 🪙`;
+    return `${medal} **${user.username}** — ${value}`;
+}
+
+/**
+ * Creates a leaderboard embed for either XP or Balance rankings
+ */
+export function getLeaderboardEmbed(leaders: LeaderboardUser[], type: 'xp' | 'balance'): EmbedBuilder {
+    const description = leaders.map((user, index) =>
+        formatLeaderEntry(user, index, type)
+    ).join("\n");
+
+    const title = type === 'xp' ? "🏆 XP Leaderboard" : "💰 Richest Players";
+
+    return new EmbedBuilder()
+        .setTitle(title)
+        .setDescription(description)
+        .setColor(0xFFD700); // Gold
+}