fix: OpenAPI spec accuracy — hide internal endpoints, mark signup/verify deprecated

- Remove @openapi annotations from /v1/billing/webhook (Stripe-internal)
- Remove @openapi annotations from /v1/billing/success (browser redirect)
- Mark /v1/signup/verify as deprecated (returns 410)
- Add 3 TDD tests in openapi-spec.test.ts
- Update 2 existing tests in app-routes.test.ts
- 530 tests passing (was 527)

dist/__tests__/api.test.js

@@ -555,6 +555,21 @@ describe("OpenAPI spec", () => {
         expect(paths).toContain("/v1/convert/markdown");
         expect(paths).toContain("/health");
     });
+    it("PdfOptions schema includes all valid format values and waitUntil field", async () => {
+        const res = await fetch(`${BASE}/openapi.json`);
+        const spec = await res.json();
+        const pdfOptions = spec.components.schemas.PdfOptions;
+        expect(pdfOptions).toBeDefined();
+        // Check that all 11 format values are included
+        const expectedFormats = ["Letter", "Legal", "Tabloid", "Ledger", "A0", "A1", "A2", "A3", "A4", "A5", "A6"];
+        expect(pdfOptions.properties.format.enum).toEqual(expectedFormats);
+        // Check that waitUntil field exists with correct enum values
+        expect(pdfOptions.properties.waitUntil).toBeDefined();
+        expect(pdfOptions.properties.waitUntil.enum).toEqual(["load", "domcontentloaded", "networkidle0", "networkidle2"]);
+        // Check that headerTemplate and footerTemplate descriptions mention 100KB limit
+        expect(pdfOptions.properties.headerTemplate.description).toContain("100KB");
+        expect(pdfOptions.properties.footerTemplate.description).toContain("100KB");
+    });
 });
 describe("404 handler", () => {
     it("returns proper JSON error format for API routes", async () => {