Add stats & leaderboard menus and lobby items

Add StatsMenu and LeaderboardMenu GUI implementations and wire them into the lobby hotbar. LobbyItemManager now builds a tutorial written-book, a player-head Profile & Stats item, and a leaderboard gold-ingot item, tags them with PDC keys, and opens the appropriate menu or book on interact. Leaderboard loads top-10 asynchronously from the stats manager. Also add corresponding language keys for item names/lores and menu titles.

src/main/resources/languages/en_US.yml

@@ -23,6 +23,15 @@ game:
       name: '<gold><bold>Kits</bold></gold> <gray>(right-click)</gray>'
     perks:
       name: '<light_purple><bold>Perks</bold></light_purple> <gray>(right-click)</gray>'
+    tutorial:
+      name: '<yellow><bold>How to Play</bold></yellow>'
+      lore: '<gray>Read me to understand the game!</gray>'
+    stats:
+      name: '<aqua><bold>Profile & Stats</bold></aqua>'
+      lore: '<gray>View your personal statistics.</gray>'
+    leaderboard:
+      name: '<gold><bold>Top 10 Leaderboard</bold></gold>'
+      lore: '<gray>Who are the best players?</gray>'
 
 ranking:
   placement_progress: '<prefix><gray>Placement <aqua><current>/<total></aqua> — Placed <aqua>#<placement></aqua> · <aqua><kills></aqua> Kill(s)</gray>'
@@ -218,6 +227,10 @@ gui:
     selected: '<green>Equipped: <perk><green>!'
     deselected: '<red>Unequipped: <perk><red>!'
     close: '<red>✕ Close</red>'
+  stats_menu:
+    title: '<aqua><bold>Profile & Stats</bold></aqua>'
+  leaderboard_menu:
+    title: '<gold><bold>Top 10 Leaderboard</bold></gold>'
 
 perks:
   oracle: