refactor: split currency and key/metal formatting into separate units

this simplifies functions and tests, and will make currency optional/variable later

__tests__/currency.test.ts

@@ -0,0 +1,17 @@
+import { describe, expect, test, jest, mock, beforeEach } from "bun:test";
+import { convertTF2PriceToUSD } from '../src/content/utils/currency'
+
+mock.module('../src/content/config', () => ({
+  conversion_ref_usd: 0.05 // Mock conversion rate
+}))
+
+
+describe('Currency Service', () => {
+  beforeEach(() => {
+    jest.clearAllMocks()
+  });
+
+  test('convertTF2PriceToUSD returns correct price', () => {
+    expect(convertTF2PriceToUSD(1, 10, 50)).toBe(3);
+  })
+})

__tests__/formatting.test.ts

@@ -16,34 +16,34 @@ describe('formatPrice', () => {
     });
 
     test('formats price with keys and metal', () => {
-        expect(formatPrice(2, 10, 50)).toBe('2.2 keys (US$5.50)');
+        expect(formatPrice(2, 10, 50)).toBe('2.2 keys');
         expect($T).toHaveBeenCalledWith('%@ keys');
     });
 
     test('formats price with metal only', () => {
-        expect(formatPrice(0, 15.75, 50)).toBe('15.75 ref (US$0.79)');
+        expect(formatPrice(0, 15.75, 50)).toBe('15.75 ref');
     });
 
     test('formats price with metal only and whole number', () => {
-        expect(formatPrice(0, 3, 50)).toBe('3 ref (US$0.16)');
+        expect(formatPrice(0, 3, 50)).toBe('3 ref');
     });
 
     test('uses singular key form', () => {
-        expect(formatPrice(1, 0, 50)).toBe('1 key (US$2.50)');
+        expect(formatPrice(1, 0, 50)).toBe('1 key');
         expect($T).toHaveBeenCalledWith('%@ key');
     });
 
     test('rounds USD up to nearest cent', () => {
-        expect(formatPrice(3, 7.33, 35)).toBe('3.21 keys (US$5.62)');  // (3 * 35 + 7.33) * 0.05 = 5.6165 → 5.62
+        expect(formatPrice(3, 7.33, 35)).toBe('3.21 keys');  // (3 * 35 + 7.33) * 0.05 = 5.6165 → 5.62
     });
 
     test('handles different locale formatting', () => {
-        expect(formatPrice(2, 10, 50, 'de')).toMatch(/2,2 keys \(US\$5,50\)/);
-        expect(formatPrice(0, 15.75, 50, 'de')).toMatch(/15,75 ref \(US\$0,79\)/);
+        expect(formatPrice(2, 10, 50, 'de')).toMatch(/2,2 keys/);
+        expect(formatPrice(0, 15.75, 50, 'de')).toMatch(/15,75 ref/);
     });
 
     test('handles zero values', () => {
-        expect(formatPrice(0, 0, 50)).toBe('0 ref (US$0.00)');
-        expect(formatPrice(0, 0, 50, 'de')).toMatch(/0 ref \(US\$0,00\)/);
+        expect(formatPrice(0, 0, 50)).toBe('0 ref');
+        expect(formatPrice(0, 0, 50, 'de')).toMatch(/0 ref/);
     });
 });