Hacker admissions emails and Tito duplicate check fix

[ReehalS]

Closes #515, #502

[Copilot]

Pull request overview

Adds hacker admissions emailing (single + bulk) into the admin invites workflow while also reducing Tito duplicate-check latency during bulk sends.

Changes:

• Introduces hacker admission invite types (accept/waitlist_accept/waitlist/reject) and corresponding single/bulk invite responses.
• Consolidates the admin invites UI into a unified InvitePanel (single + bulk) shared across hackers/judges/mentors/volunteers.
• Optimizes Tito duplicate handling by prefetching existing RSVP invitations into an email→URL map and reusing URLs when possible.

Reviewed changes

Copilot reviewed 24 out of 24 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
app/_types/emails.ts	Adds hacker admission types, labels, and response/result types used across UI + server actions.
app/(pages)/admin/invites/page.tsx	Updates invites page to include Hackers tab and use the consolidated InvitePanel.
app/(pages)/admin/_components/InvitePanel/InvitePanel.tsx	New shared panel for single/bulk invite flows across roles (with Tito config fetching).
app/(pages)/admin/_components/InvitePanel/SingleInviteForm.tsx	New unified single-invite form including hacker admission decision handling.
app/(pages)/admin/_components/InvitePanel/BulkInviteForm.tsx	New unified bulk-invite form including hacker CSV Type column + result downloads.
app/(pages)/admin/_utils/generateInviteResultsCSV.ts	Adds optional admission Type column support for results export.
app/(pages)/admin/_utils/generateInviteFailuresCSV.ts	Adds optional Type column in failures export to enable re-upload for retries.
app/(api)/_actions/emails/sendSingleHackerInvite.ts	Implements server action for single hacker admissions emails (email-only vs Tito+Hub).
app/(api)/_actions/emails/sendBulkHackerInvites.ts	Implements server action for bulk hacker admissions emails using custom CSV parser.
app/(api)/_actions/emails/parseHackerAdmissionsCSV.ts	Adds CSV parsing/validation for hacker admissions (Type column).
app/(api)/_actions/emails/processBulkInvites.ts	Allows swapping the default CSV parser with a custom parser per bulk flow.
app/(api)/api/admissions/hackers/route.ts	Adds an authenticated admissions API endpoint for batch sending hacker emails.
app/(api)/_actions/tito/getAllRsvpInvitations.ts	New helper to prefetch all RSVP invitations for duplicate short-circuiting.
app/(api)/_actions/tito/getOrCreateTitoInvitation.ts	Extends Tito invite creation to accept a prefetched invitation map for faster duplicate handling.
app/(api)/_actions/emails/sendBulkMentorOrVolunteerInvites.ts	Uses prefetched Tito invitations map to reduce duplicate-check latency.
app/(api)/_actions/emails/transporter.ts	Makes Nodemailer transporter lazily initialized and exports DEFAULT_SENDER for guards.
app/(api)/_actions/emails/emailTemplates/2026HackerInviteTemplate.ts	Adds 2026 hacker acceptance email template.
app/(api)/_actions/emails/emailTemplates/2026HackerWaitlistAcceptTemplate.ts	Adds 2026 hacker waitlist-accept template.
app/(api)/_actions/emails/emailTemplates/2026HackerWaitlistTemplate.ts	Adds 2026 hacker waitlist template.
app/(api)/_actions/emails/emailTemplates/2026HackerRejectionTemplate.ts	Adds 2026 hacker rejection template.
Deleted legacy judge/mentor/volunteer invite form components	Removes now-redundant per-role invite forms replaced by InvitePanel.

Comments suppressed due to low confidence (2)

app/(pages)/admin/_components/InvitePanel/InvitePanel.tsx:59

• When role changes to a Tito-required role, the effect starts fetching RSVP lists/releases but loading isn't set back to true. This can render SingleInviteForm/BulkInviteForm with empty rsvpLists/releases briefly and allow interaction before data is loaded. Consider setting setLoading(true) at the start of the effect (when needsTito(role)), and optionally clearing loadError/data when switching roles.
  app/(api)/_actions/tito/getOrCreateTitoInvitation.ts:56
• The comment says duplicate recovery is only for the single-invite path (no pre-fetched map), but the recovery logic runs even when existingInvitationsMap is provided (it triggers on any duplicate error). Either update the comment to match the behavior, or gate the recovery behind !existingInvitationsMap if the intent is to avoid per-email lookups in bulk sends.

  // Duplicate recovery for single-invite path (no pre-fetched map)
  if (!titoResponse.ok && isDuplicateTicketError(titoResponse.error)) {
    console.warn(`[Tito] Duplicate detected for ${email}, attempting recovery`);

    const existingRes = await getRsvpInvitationByEmail(rsvpListSlug, email);

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[ReehalS]

@michelleyeoh ready for merge now

[michelleyeoh]

LGTM