feat(ExcelIO): add ExcelMapRegistry for DI integration

NEW/src/JdeScoping.ExcelIO/Mapping/ExcelMapRegistry.cs

@@ -0,0 +1,45 @@
+namespace JdeScoping.ExcelIO.Mapping;
+
+/// <summary>
+/// Registry for Excel class maps, used for DI and lookup.
+/// </summary>
+public sealed class ExcelMapRegistry
+{
+    private readonly Dictionary<Type, IExcelClassMap> _maps = new();
+
+    /// <summary>
+    /// Registers a map for a type.
+    /// </summary>
+    public void Register<T>(ExcelClassMap<T> map)
+    {
+        _maps[typeof(T)] = map;
+    }
+
+    /// <summary>
+    /// Gets the map for a type.
+    /// </summary>
+    public IExcelClassMap GetMap<T>() => GetMap(typeof(T));
+
+    /// <summary>
+    /// Gets the map for a type.
+    /// </summary>
+    public IExcelClassMap GetMap(Type type)
+    {
+        if (_maps.TryGetValue(type, out var map))
+            return map;
+
+        throw new InvalidOperationException(
+            $"No Excel map registered for type {type.Name}. " +
+            $"Register a map using ExcelMapRegistry.Register().");
+    }
+
+    /// <summary>
+    /// Checks if a map exists for a type.
+    /// </summary>
+    public bool HasMap<T>() => HasMap(typeof(T));
+
+    /// <summary>
+    /// Checks if a map exists for a type.
+    /// </summary>
+    public bool HasMap(Type type) => _maps.ContainsKey(type);
+}