Feature/94 user registrations tab

[Jxl-s]

Closes #94

Overview

New /registrations page (role=user only) listing services the user is registered for — programs from service_bookings, private lessons from coaching_sessions — grouped by service, with registered children shown per service card. Read-only.

Also extracted duplicated serviceTypeLabel / DAY_NAMES into lib/service-labels.ts.

Deferred (blocked on follow-up PR): sidebar entry + post-login redirect. Page is currently reachable only by direct URL.

Testing

Manual, as jane@doe.com (role=user), seeded with 1 adult program + 1 private lesson + 1 child program with 2 kids:

• All 3 cards render, filter tabs work, multi-child grouping displays correctly.
• Admin/logged-out access to /registrations redirects as expected.
• /memberships unaffected (regression check on middleware guard).

tsc and eslint clean. No unit tests added — repo has no page-level test scaffolding and this PR ships no mutation code.

Screenshots / Screencasts

Checklist

• Code is neat, readable, and works
• Code is commented where appropriate and well-documented
• Commit messages follow our guidelines
• Issue number is linked
• Branch is linked
• Reviewers are assigned (one of your tech leads)

Notes

• Acceptance criterion 1 only fully closes once the sidebar/redirect PR lands.
• Middleware has a TODO marking the guard for replacement by that PR.
• No cache on the per-user query — deliberate, since there's no mutation code here to invalidate from.