Restore resume uploads during registration

[joshuasilva414]

What to build

Fix the test-web registration flow so an applicant can upload a resume without encountering an error that the HackKit runtime has not been initialized. The completed registration must retain the uploaded resume reference and present a clear upload failure when one occurs.

Acceptance criteria

• A new applicant can submit registration with an optional valid PDF resume using the configured local blob adapter.
• The registration flow initializes and uses the HackKit runtime correctly for the upload path.
• On a successful upload and registration, the hacker record contains the uploaded resume reference.
• Upload or registration failures are shown to the applicant with actionable feedback and do not leave a misleading successful state.
• An automated integration test or repeatable end-to-end verification covers the registration upload path.

Blocked by

None - can start immediately

[linear-code]

HK-247