feat: Story 021 — Check-in Lists and Gates

[iagocavalcante]

Summary

Implements Story 021: Check-in Lists and Gates — configurable check-in lists and gates for controlling entry at different venue points.

Base: PR #52 (Story 020 — Check-in)

• Check-in Lists — organizers create lists with item filtering and optional time windows (e.g. "VIP Entrance" restricted to 08:00–10:00 with only VIP tickets)
• Gates — physical entry points linked to check-in lists (e.g. "North Door" → General Entrance list)
• Multi-list tickets — same ticket can be checked in independently on different lists
• Gate-scoped check-in — operators select a gate, scanner/search scopes to that gate's lists
• List/gate CRUD — full admin config page with modal forms for creating/editing
• Time restrictions — check-in blocked outside configured time window
• Item validation — tickets not on a gate's lists are rejected with clear error

Files changed (15 files, ~1,334 lines)

Area	Files
Database	Migration: 4 new tables + check_ins index update
Schemas	CheckInList, CheckInListItem, Gate, GateCheckInList
Context	Extended CheckIns with CRUD + list-scoped check-in + gate check-in
Config UI	CheckInConfigLive — lists/gates management with modals
Check-in UI	Gate selector dropdown, new error messages
Navigation	Config link on event show + check-in pages
Tests	16 new tests (CRUD + list-scoped + gate check-in)

Closes #21

Test plan

• All 1503 tests pass (0 failures)
• Compilation clean with --warnings-as-errors
• Manual: Create check-in list with items and time restriction
• Manual: Create gate linked to check-in list
• Manual: Gate selector appears on check-in page
• Manual: Scan rejects ticket not on gate's list
• Manual: Same ticket checks in on different lists independently
• Manual: Time-restricted list blocks check-in outside window