Rework shop to support multiple item types and add unified PlayerModel

Generalize the shop from selling only ModifierDefinition to any IShopItem
(modifiers + dice). Add purchase condition checks, hover tooltips, and
fixed prices. Introduce PlayerModel as a facade over CurrencyBank,
InventoryModel, and DiceCollection for centralized state and save/load.

New files:
- IShopItem interface for purchasable items
- ShopCatalog SO (unified catalog for all item types)
- ShopTooltipView (description on hover)
- PlayerModel (aggregates player state)
- DiceCollection (owned dice tracking)
- DiceCatalog SO (dice definition registry)
- DiceCollectionTests

Modified:
- ModifierDefinition/DieDefinitionSO implement IShopItem
- ShopModel/ShopView/ShopItemView/ShopController use IShopItem
- SaveData v3 with OwnedDiceIds
- GameController uses PlayerModel for save/load
- GameLifetimeScope registers new services

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Assets/Scripts/Player/PlayerModel.cs

@@ -0,0 +1,29 @@
+using System;
+using YachtDice.Economy;
+using YachtDice.Inventory;
+
+namespace YachtDice.Player
+{
+    public class PlayerModel
+    {
+        public CurrencyBank Currency { get; }
+        public InventoryModel Inventory { get; }
+        public DiceCollection Dice { get; }
+
+        public event Action OnChanged;
+
+        public PlayerModel(
+            CurrencyBank currencyBank,
+            InventoryModel inventory,
+            DiceCollection diceCollection)
+        {
+            Currency = currencyBank;
+            Inventory = inventory;
+            Dice = diceCollection;
+
+            currencyBank.OnBalanceChanged += _ => OnChanged?.Invoke();
+            inventory.OnInventoryChanged += () => OnChanged?.Invoke();
+            diceCollection.OnChanged += () => OnChanged?.Invoke();
+        }
+    }
+}