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/Shop/IShopItem.cs

@@ -0,0 +1,23 @@
+using UnityEngine;
+
+namespace YachtDice.Shop
+{
+    /// <summary>
+    /// Any item that can appear in the shop.
+    /// Implemented by ScriptableObject definitions (ModifierDefinition, DieDefinitionSO).
+    /// </summary>
+    public interface IShopItem
+    {
+        string Id { get; }
+        string DisplayName { get; }
+        string Description { get; }
+        Sprite Icon { get; }
+        int ShopPrice { get; }
+
+        /// <summary>
+        /// Whether this item can be repurchased after being owned (e.g. consumable modifiers).
+        /// If false, the shop marks it as "Owned" once purchased.
+        /// </summary>
+        bool IsRepurchasable { get; }
+    }
+}