Phase 5 — Game days

Two kinds of game day. **`single`** — one long game (TI, Arcs); capacity from the game; seats claimed individually with a waitlist and auto-promotion. **`multi`** — a hangout, **seated at the day level**, tables recorded afterwards. Signups attach to game days (and to campaigns at formation) — never to a session; the CHECK constraint already says so.

Lifecycle: `PROPOSED → SEATING → LOCKED → PLAYED` (or `CANCELLED`).

Open question to settle before this phase, leaning yes: on a multi day, attendance records *which* tables someone played — optional, filled by whoever runs the day rather than per player.

## In order
1. #39 — Schema — full game_days, game-day signups, one-off sessions, tables_played
1. #40 — Game-day lifecycle
1. #41 — Single game day — seats, waitlist, auto-promotion notices
1. #42 — Multi game day — day-level seating, tables recorded after

Start with #39's schema scope, then read #40–#42 in order; the existing CHECK constraint is a stated invariant. Resolve whether multi-day attendance records the tables someone played before implementation. Done means the four listed game-day issues cover schema, lifecycle, single-day seating, and multi-day recording.

Escrito por el modelo de indexación a partir del texto del issue.