feat: walk-in queue for hackathon day check-in

[5sansiva]

Walk-In Queue

Adds a FIFO walk-in queue for at-event registration. Applicants who arrive at the door can be scanned in, placed in a queue, and promoted to accepted by a super admin.

State Machine

[any status] → walk-in scan → waitlisted (+ queue position) → promote → accepted → check-in scan

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Database

• 000020_add_walk_ins — New walk_ins table with a FIFO index (queued_at ASC, id ASC) to enforce arrival order.
• 000021_add_walkin_scan_type — Seeds the walk_in scan type into the settings table.

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Backend

Store (internal/store/)

• walkins.go — Core queue operations: Enqueue, PromoteNext, GetQueue, GetStatusByUserID.
• storage.go — WalkIns interface added to the Storage interface.
• applications.go — GetStatusByUserID added to short-circuit users who are already accepted.
• mock_store.go — Mocks for all new WalkIns methods.

Handlers (cmd/api/)

• walkins.go — Two new super admin endpoints:
  • GET /superadmin/walk-ins — Returns the current queue.
  • POST /superadmin/walk-ins/promote — Promotes the next N applicants, triggering acceptance emails.
• scans.go — Updated createScanHandler to detect the walk_in scan category, enqueue the user, flip their application status to waitlisted, send a queued email, and short-circuit if the user is already accepted.
• api.go — Routes wired for /superadmin/walk-ins.
• scans_test.go, walkins_test.go — Test coverage for scan and promote flows.

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Mailer

• SendWalkInQueuedEmail — Sends the hacker their queue position on scan (SendGrid + SMTP).
• SendWalkInAcceptedEmail — Sends the hacker their acceptance confirmation and QR code on promotion (SendGrid + SMTP).
• walk_in_queued.html, walk_in_accepted.html — Email templates (copy TBD from ops).

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Frontend

• pages/superadmin/walk-in-queue/ — Walk-In Queue page with a live FIFO table, 30-second auto-refresh, and pending/total counts.
• PromoteDialog — Super admin enters N to promote the next N walk-ins; triggers acceptance emails.
• WalkInQueueTable — Displays queue position, email, and arrival time for each applicant.
• routes.tsx — Route added at /admin/sa/walk-in-queue (super admin only).
• AppSidebar.tsx — Walk-In Queue added to the super admin nav.
• Scan types updated to support the walk_in category with a distinct icon, color, and validation.

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Testing

• scans_test.go — Covers walk-in scan detection, enqueue logic, status flip, and already-accepted short-circuit.
• walkins_test.go — Covers queue retrieval and promote flows.

[NoelVarghese2006]

It the plan file really necessary? Should we also make a dedicated folder for it?

[5sansiva]

I kept the plan file just so if any further changes or checks are needed we can update, also just so we can update the docs with this plan as well

[NoelVarghese2006]

why the change?

[5sansiva]

ai slipup there, I can fix that part