Add transfer tracking and secure admin access

backend/MiaoJiZhang.Domain/Enums/Enums.cs

@@ -17,12 +17,49 @@ public enum AppMode
 }
 
 /// <summary>账单类型</summary>
-public enum TransactionType
+public enum TransactionType
 {
     Expense = 0,
     Income = 1,
     Transfer = 2,
-}
+}
+
+public enum TransferDirection
+{
+    In = 0,
+    Out = 1,
+}
+
+public static class TransactionTypeRules
+{
+    public static bool IsExpense(this TransactionType type, TransferDirection? direction = null) =>
+        type == TransactionType.Expense ||
+        type == TransactionType.Transfer && direction == TransferDirection.Out;
+
+    public static bool IsIncome(this TransactionType type, TransferDirection? direction = null) =>
+        type == TransactionType.Income ||
+        type == TransactionType.Transfer && direction == TransferDirection.In;
+
+    public static TransactionType CategoryType(
+        this TransactionType type,
+        TransferDirection? direction = null) => type == TransactionType.Transfer
+        ? direction == TransferDirection.In ? TransactionType.Income : TransactionType.Expense
+        : type;
+
+    public static string ToWire(this TransactionType type) => type switch
+    {
+        TransactionType.Income => "income",
+        TransactionType.Transfer => "transfer",
+        _ => "expense",
+    };
+
+    public static string? ToWire(this TransferDirection? direction) => direction switch
+    {
+        TransferDirection.In => "in",
+        TransferDirection.Out => "out",
+        _ => null,
+    };
+}
 
 /// <summary>账单来源（决策：AI 记账可追溯）</summary>
 public enum TransactionSource