refactor(backend): final cleanup pass

- re-register WebAuthn passkey routes (registration was dropped in the
  #1054 merge, breaking passkey login) and document all six endpoints
- delete utils/simple-db-ops.ts (last caller migrated to DataCrypto)
- starter: use the typed serverReady export, collapse the four-way
  version lookup to env then package.json candidates
- add OpenAPI JSDoc to c2s-tunnel-presets endpoints
- strip block-divider comment banners

src/backend/tests/database/routes/host-enrollment-auth.test.ts

@@ -4,9 +4,9 @@ const mocks = vi.hoisted(() => ({
   isUserDataUnlocked: vi.fn(),
 }));
 
-vi.mock("../../../utils/simple-db-ops.js", () => ({
-  SimpleDBOps: {
-    isUserDataUnlocked: mocks.isUserDataUnlocked,
+vi.mock("../../../utils/data-crypto.js", () => ({
+  DataCrypto: {
+    canUserAccessData: mocks.isUserDataUnlocked,
   },
 }));