feature: tournament check-in, free agents, join rules and stats leaderboard

[lukepolo]

Frontend for the tournament features in 5stackgg/api#403.

Surfaces

Registration step — new 5th step in the create wizard, between Location and Match Options, reused on the settings tab. Who can register (Teams / Free Agents / Both), minimum role, ELO range, preferred regions, invite-only + passcode.

Check-In settings — off by default, collapsed to a single switch until enabled. Mode selector, both offsets, a visual opens → closes → start timeline, and the schedule freeze once the window opens.

Check-In panel — participant-facing, six states: before registering, not open, open, players mode, checked in, missed. Reuses CheckInDeadline so urgent/critical countdown states come for free.

Check-In Review — organizer hold panel: missed teams with roster size and registration age, Re-admit per team, Extend check-in, Continue without them.

Free Agents tab — pool ordered by sign-up time, sign up / leave, organizer Regenerate Teams and drafted-team preview. Surfaces the case where a high-ELO player is waitlisted for signing up late, rather than hiding it.

Stats tab — tournament leaderboard with a hairline stat ribbon, sorted server-side.

Notes

• CheckInReview added to four status-filter inclusion lists so a held tournament doesn't vanish from the listings — including /tournaments/manage, the screen an organizer would use to fix it.
• roleOrder is now exported from AuthStore so the client has one role ladder instead of two.
• regions and check_in_setting already exist on match_options and the wizard shares one form, so tournament values bind as registration_regions / team_check_in_setting and are translated back on write.
• 143 new i18n keys across all 17 locales; check-translations reports 16/16.