feat(budget): aylık bütçe motoru, limitler ve ay sonu tahmini

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

src/shared/schemas/budget.ts

@@ -0,0 +1,29 @@
+import { z } from "zod";
+import { tr } from "../../i18n/tr";
+import { nonNegativeMoneySchema } from "./account";
+
+/** Bütçe ayı "YYYY-MM". */
+export const budgetMonthSchema = z
+  .string()
+  .regex(/^\d{4}-(0[1-9]|1[0-2])$/, tr.budget.validation.month);
+
+/**
+ * Limit formu: kategori → tutar metni. Boş veya 0 limit kaldırılır (kategori bütçesiz olur).
+ */
+export const budgetLimitsSchema = z.object({
+  month: budgetMonthSchema,
+  limits: z
+    .array(
+      z.object({
+        categoryId: z.string().regex(/^[a-f0-9]{24}$/i, tr.budget.validation.category),
+        amount: nonNegativeMoneySchema,
+      }),
+    )
+    .max(500)
+    .transform((list) =>
+      list
+        .filter((l) => l.amount > 0)
+        .map((l) => ({ categoryId: l.categoryId, amountMinor: l.amount })),
+    ),
+});
+export type BudgetLimitsForm = z.output<typeof budgetLimitsSchema>;