refactor: extract buildPdfOptions to DRY up renderPdf/renderUrlPdf (TDD)

- Extract shared PDF options construction into buildPdfOptions()
- Both renderPdf and renderUrlPdf now use the shared builder
- 5 TDD tests added (pdf-options-builder.test.ts)
- 633 tests passing, 0 tsc errors

src/__tests__/setup.ts

@@ -53,7 +53,10 @@ vi.mock("../services/keys.js", () => {
 });
 
 // Mock browser service
-vi.mock("../services/browser.js", () => ({
+vi.mock("../services/browser.js", async (importOriginal) => {
+  const actual = await importOriginal<Record<string, unknown>>();
+  return {
+  buildPdfOptions: actual.buildPdfOptions,
   initBrowser: vi.fn().mockResolvedValue(undefined),
   closeBrowser: vi.fn().mockResolvedValue(undefined),
   renderPdf: vi.fn().mockResolvedValue({ pdf: Buffer.from("%PDF-1.4 mock pdf content here"), durationMs: 10 }),
@@ -68,7 +71,8 @@ vi.mock("../services/browser.js", () => ({
     uptimeMs: 10000,
     browsers: [],
   }),
-}));
+};
+});
 
 // Mock verification service
 vi.mock("../services/verification.js", () => ({