[Add] Universal modifier system, shop, inventory & persistence

Replace hardcoded BonusForOnes/MultiplierForSixes with data-driven
modifier system supporting 2 scopes (SelectedCategory, AnyCategoryClosed),
4 effect types, durability modes (Permanent, LimitedUses), and
configurable targets via ScriptableObject (ModifierData).

- Modifier domain: ModifierEnums, ModifierTarget, ModifierData,
  ModifierRuntime, ModifierEffect (dict-based strategy), ModifierPipeline
  (4-pass: cat-additive → cat-multiplicative → final-additive → final-multiplicative)
- ScoringSystem: replaced old modifier list with ModifierPipeline integration,
  added OnCategoryConfirmed event
- Shop MVC: ShopCatalog (SO), ShopModel, ShopView, ShopItemView, ShopController
- Inventory MVC: InventoryModel (activate/deactivate/sell/durability),
  InventoryView, InventorySlotView, InventoryController
- CurrencyBank: editor-adjustable balance with events
- Persistence: SaveData + SaveSystem (Newtonsoft JSON + PlayerPrefs)
- Editor: ModifierAssetCreator menu item to generate 6 example modifiers + catalog
- Tests: 6 test classes covering effects, pipeline, scoring, shop, inventory, save
- GameController: wired shop/inventory/save lifecycle
- GameInfoView: added currency display, shop/inventory toggle buttons

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

Assets/Scripts/Persistence/SaveSystem.cs

@@ -0,0 +1,42 @@
+using Newtonsoft.Json;
+using UnityEngine;
+
+public static class SaveSystem
+{
+    private const string SaveKey = "YachtDice_SaveData";
+
+    public static void Save(SaveData data)
+    {
+        string json = JsonConvert.SerializeObject(data, Formatting.Indented);
+        PlayerPrefs.SetString(SaveKey, json);
+        PlayerPrefs.Save();
+    }
+
+    public static SaveData Load()
+    {
+        if (!PlayerPrefs.HasKey(SaveKey))
+            return new SaveData();
+
+        string json = PlayerPrefs.GetString(SaveKey);
+
+        try
+        {
+            return JsonConvert.DeserializeObject<SaveData>(json) ?? new SaveData();
+        }
+        catch (JsonException e)
+        {
+            Debug.LogWarning($"Failed to deserialize save data, returning default: {e.Message}");
+            return new SaveData();
+        }
+    }
+
+    public static void Delete()
+    {
+        PlayerPrefs.DeleteKey(SaveKey);
+    }
+
+    public static bool HasSave()
+    {
+        return PlayerPrefs.HasKey(SaveKey);
+    }
+}