feat(events): RSVP enrollment end-to-end

[danielhe4rt]

Parent

#237

What to build

Implement the RSVP enrollment flow end-to-end: participant clicks "Confirm presence" → system creates enrollment with status confirmed → transition is recorded in audit trail → participant sees their enrollment in the App panel.

Action: EnrollUserAction

• Accepts event + user + enrollment method context
• For rsvp and rsvp_checkin methods: creates enrollment with status confirmed (capacity validation comes in the next slice)
• Wraps in DB::transaction
• Records transition in events_enrollment_transitions (from_status=null, to_status=confirmed, triggered_by=user)
• Returns the created enrollment

Domain event (fire-and-forget, for future listeners):

• Dispatches EnrollmentConfirmed implementing ShouldDispatchAfterCommit
• Payload: enrollment_id, event_id, user_id, xp_reward_rsvp (from policy)
• No listener in this slice — just the event dispatch

App panel (participant view):

• "My Events" page listing user's enrollments with status badges
• Event detail page with "Confirm Presence" button (visible when enrollment_method is rsvp or rsvp_checkin and user is not yet enrolled)
• Button dispatches EnrollUserAction

Admin panel (organizer view):

• Enrollments RelationManager on Event resource showing all enrollments with status, enrolled_at
• Read-only for now (management actions come in later slices)

Validation rules:

• User cannot enroll twice in same event (UNIQUE constraint)
• Event must be active and not past (starts_at > now())
• Enrollment method must be rsvp or rsvp_checkin (application flow is a separate slice)

Acceptance criteria

• Participant can RSVP to an event from the App panel
• Enrollment is created with status confirmed and enrolled_at timestamp
• Transition record is written to events_enrollment_transitions
• EnrollmentConfirmed domain event is dispatched after transaction commit
• Duplicate enrollment attempt returns appropriate error (409 or validation error)
• Enrolling in a past event is rejected
• Admin panel shows enrollments per event
• Participant sees their enrollments in "My Events" page
• Feature tests cover: successful enrollment, duplicate prevention, past event rejection
• Pint passes

Blocked by

• Events: Foundation — schema, models, enum, Admin CRUD #239 (Foundation)