feat(transactions): işlem servisi, bakiye hesaplama, satıcı kuralları ve izolasyon

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/models/payee.ts

@@ -0,0 +1,25 @@
+import { model, models, Schema, type InferSchemaType, type Model } from "mongoose";
+import { TRANSACTION_TYPES } from "@/shared/transactions";
+
+/** Satıcı / karşı taraf ve "akıllı giriş" kuralı: son kullanılan kategori ve hesap (Bölüm 6.3). */
+const payeeSchema = new Schema(
+  {
+    householdId: { type: Schema.Types.ObjectId, required: true },
+    name: { type: String, required: true, trim: true, maxlength: 80 },
+    nameKey: { type: String, required: true },
+    lastType: { type: String, enum: TRANSACTION_TYPES, default: "expense" },
+    lastCategoryId: { type: Schema.Types.ObjectId, default: null },
+    lastAccountId: { type: Schema.Types.ObjectId, default: null },
+    useCount: { type: Number, default: 0 },
+    lastUsedAt: { type: Date, default: () => new Date() },
+  },
+  { timestamps: true, collection: "payees" },
+);
+
+payeeSchema.index({ householdId: 1, nameKey: 1 }, { unique: true });
+payeeSchema.index({ householdId: 1, useCount: -1 });
+
+export type Payee = InferSchemaType<typeof payeeSchema>;
+
+export const PayeeModel: Model<Payee> =
+  (models.Payee as Model<Payee> | undefined) ?? model<Payee>("Payee", payeeSchema);