feat(shared): para, miktar ve İstanbul günü yardımcıları

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

src/shared/quantity.test.ts

@@ -0,0 +1,40 @@
+import { describe, expect, it } from "vitest";
+import { convertQuantity, formatQuantity, parseQuantity } from "./quantity";
+
+describe("parseQuantity", () => {
+  it.each([
+    ["1,5", 1500],
+    ["1.5", 1500],
+    ["2", 2000],
+    ["0,125", 125],
+    ["5", 5000],
+    [" 10,25 ", 10250],
+  ])("%s → %i", (input, expected) => {
+    expect(parseQuantity(input)).toBe(expected);
+  });
+
+  it.each(["", "-1", "1,2345", "1,2,3", "abc", "1e3"])("geçersiz: %s", (input) => {
+    expect(parseQuantity(input)).toBeNull();
+  });
+});
+
+describe("formatQuantity", () => {
+  it("gereksiz sıfırları atar, birim ekler", () => {
+    expect(formatQuantity(1500, "kg")).toBe("1,5 kg");
+    expect(formatQuantity(5000, "gr")).toBe("5 gr");
+    expect(formatQuantity(125)).toBe("0,125");
+    expect(formatQuantity(1234500)).toBe("1.234,5");
+    expect(formatQuantity(-250)).toBe("-0,25");
+  });
+});
+
+describe("convertQuantity", () => {
+  it("aynı boyutta dönüştürür", () => {
+    expect(convertQuantity(1500, "kg", "g")).toBe(1500000); // 1,5 kg = 1500 g
+    expect(convertQuantity(500000, "g", "kg")).toBe(500); // 500 g = 0,5 kg
+    expect(convertQuantity(2000, "lt", "ml")).toBe(2000000);
+  });
+  it("uyumsuz birimde hata verir", () => {
+    expect(() => convertQuantity(1000, "kg", "lt")).toThrow(RangeError);
+  });
+});