refactor: enforce enum machine codes #18

Use owner enums for known codes; preserve wire values and unknown fallbacks.

Verified npm ci and verify: 379 tests, 5 lint checks, app and Storybook builds.

src/shared/api/index.ts

@@ -9,7 +9,7 @@ export {
 	invalidateApiRequests,
 } from "./client";
 export type { paths } from "./generated/schema";
-export { apiErrorCode } from "./problem-details";
+export { ApiErrorCode, apiErrorCode, isApiErrorCode } from "./problem-details";
 
 export {
 	invalidateResourceAccess,