Extend VContainer DI: eliminate manual composition and duplicate references

- Register InventoryModel, ShopModel as container-managed singletons
- Register GameController, ShopController, InventoryController via RegisterComponent
- Replace [SerializeField] with [Inject] for service dependencies in controllers
- Move maxActiveModifierSlots config to GameLifetimeScope (composition root)
- Remove manual model creation and Initialize() calls from GameController
- Add ToggleVisibility() to ShopController/InventoryController, removing GetComponentInChildren
- Move event subscriptions from Awake to Start for safe VContainer injection order
- Transfer game startup orchestration to GameController.Start()

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

Assets/Scripts/Game/GameManager.cs

@@ -1,5 +1,6 @@
 using System;
 using UnityEngine;
+using VContainer;
 using YachtDice.Categories;
 using YachtDice.Scoring;
 
@@ -7,13 +8,12 @@ namespace YachtDice.Game
 {
     public class GameManager : MonoBehaviour
     {
-        [Header("References")]
-        [SerializeField] private DiceManager diceManager;
-        [SerializeField] private ScoringSystem scoringSystem;
-
         [Header("Settings")]
         [SerializeField] private int maxRollsPerTurn = 3;
 
+        private DiceManager diceManager;
+        private ScoringSystem scoringSystem;
+
         public int CurrentRoll { get; private set; }
         public int CurrentTurn { get; private set; }
 
@@ -26,9 +26,11 @@ namespace YachtDice.Game
         public event Action<CategoryDefinition, int> OnScored;
         public event Action<int> OnGameOver;
 
-        private void Start()
+        [Inject]
+        public void Construct(DiceManager diceManager, ScoringSystem scoringSystem)
         {
-            StartNewGame();
+            this.diceManager = diceManager;
+            this.scoringSystem = scoringSystem;
         }
 
         public void StartNewGame()