[Rename] Unify Die → Dice naming across the entire project

Standardize all class, interface, file, method, event, field, and variable
names from the inconsistent "Die" form to "Dice", matching the existing
DiceManager/DiceCatalog/DiceCollection convention.

Renamed files (7 + meta): IDie→IDice, DieInstance→DiceInstance,
DieDefinitionSO→DiceDefinitionSO, StandardDieSO→StandardDiceSO,
DieValueCondition→DiceValueCondition, AddPerDieEffect→AddPerDiceEffect,
MultiplyPerDieEffect→MultiplyPerDiceEffect.

Updated all 31 consumer and test files with matching reference changes.

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

Assets/Scripts/Dice/IDice.cs

@@ -0,0 +1,15 @@
+namespace YachtDice.Dice
+{
+    /// <summary>
+    /// Минимальный контракт для любого дайса.
+    /// Каждый дайс всегда имеет текущее значение (верхняя грань) и определение типа.
+    /// </summary>
+    public interface IDice
+    {
+        /// <summary>Текущее значение верхней грани.</summary>
+        int Value { get; }
+
+        /// <summary>Определение типа дайса (ScriptableObject).</summary>
+        DiceDefinitionSO Definition { get; }
+    }
+}