- Backend `/signup` endpoint returns 200 OK with an empty body (`TypedResults.Ok()`), causing `res.json()` to throw 'Unexpected end of JSON input'. Removed the `res.json()` return.
- Added Suspense boundary in login page to fix `useSearchParams` build error.
- Bypass NextAuth OIDC discovery with explicit token/userinfo endpoints using internal Docker DNS, avoiding 'issuer string did not match' errors.
- Fix next.config.ts API route interception that incorrectly forwarded NextAuth routes to backend by using 'fallback' rewrites.
- Add 'Use different credentials' button to login page and AuthGuard for clearing stale sessions.
The signup/cancel endpoints were passing the Keycloak sub claim (external UUID)
directly as MemberId, but ShiftSignup.MemberId references the internal Member.Id.
Now ShiftService resolves ExternalUserId to the internal Member.Id before creating
the signup record. Integration tests updated to seed proper Member entities.
