feat: include email in GET /volunteer list response

[nadavosa]

Context

The FE volunteer list view (PR need4deed-org/fe#500) adds a flat table view that includes an email column. Currently ApiVolunteerGetList does not expose email, so the column renders as "—".

Required

Add email to the volunteer list API response (GET /volunteer) so the SDK type ApiVolunteerGetList includes it.

Notes

@ivannissimrch please clarify:

• Which email field should be returned (primary contact email, user account email, or both)?
• Any privacy/permission considerations for exposing email in the list endpoint?

[ivannissimrch]

What FE needs:

• BE: the GET /volunteer endpoint should include the email for each volunteer in its response. The email already exists in the system, the single-fetch endpoint (GET
  /volunteer/:id) Returns it under person.email. We just need it included when we fetch the full list.
• SDK: the ApiVolunteerGetList type needs the email field added too, so FE knows about it at compile time.

Which email: the same one shown on the volunteer profile page (the only email field on ApiPersonGet).

Privacy: email is already visible on the profile page, GET /volunteer uses the same auth, so no new access surface.

Once both ship, FE swaps the hardcoded — for volunteer.email.