Fix leaderboard live updates across connection and bingo flows

[rxmox]

Summary

The leaderboard was not updating live for several state changes. After tracing the Pusher path end-to-end, three classes of bugs were fixed plus the missing mobile wiring for bingo line completion.

Bugs fixed

• Empty Pusher payloads on connection create (by-emails) and delete. Both endpoints called pusher.trigger(..., \"leaderboard-updated\", {}). The web client's handler checks payload.participantId and payload.connectionsCount, both undefined on an empty payload, and falls into its drop branch — so the leaderboard silently ignored the event. Now both endpoints emit a full payload per affected participant.
• Frontend sort missed tiebreakers.Leaderboard.tsx sorted only by connectionsCount, while the backend GET sorts by (completed, linesCompleted desc, connectionsCount desc). After live updates, the order would diverge from a refresh. Frontend sort now mirrors the backend.
• Bingo line completion never reached the leaderboard. No client called PUT /leaderboard/score, so linesCompleted was stuck at 0 in practice. Mobile's handleAssign now fires the score update (with the blackout completed flag) after each assignment.

Refactor

Extracted emitLeaderboardUpdate(eventId, participantId) helper. It recomputes the participant's connectionsCount, emits the full payload to event-{eventId}, and logs Pusher errors instead of throwing — so a flaky Pusher call can't 500 the originating request. Replaced four inline emit blocks with helper calls.

Files

• `shatter-backend/src/utils/leaderboard_pusher.ts` (new)
• `shatter-backend/src/controllers/leaderboard_controller.ts` — uses helper
• `shatter-backend/src/controllers/participant_connections_controller.ts` — three call sites (create, by-emails, delete) all emit full payloads
• `shatter-web/src/components/Leaderboard.tsx` — sort tiebreakers
• `shatter-mobile/src/api/games/game.api.tsx` — `UpdateLeaderboardScoreApi`
• `shatter-mobile/src/components/games/NameBingo.tsx` — fire-and-forget score update inside `handleAssign`

Verification

Backend was exercised end-to-end against a local stack:

• REST: full lifecycle (signup → create event → join → connect → score → delete → by-emails reconnect) returned correct shapes and counts; the GET sort matched expectations.
• Pusher delivery: a node subscriber on `event-{eventId}` confirmed every mutation produced exactly the right number of `leaderboard-updated` events with full payloads. Connection create/delete fire two events (one per participant); score updates fire one.
• Frontend logic: a headless port of the React component (initial fetch + filter, Pusher merge, sort) was driven through the same mutation sequence; every state snapshot matched expected, including the `/by-emails` path that previously dropped events and the `completed` tiebreaker putting Alice above Bob despite a lower `connectionsCount`.
• Builds: `shatter-backend` (`tsc`) and `shatter-web` (`tsc -b && vite build`) both clean. Mobile typecheck shows no new errors in touched files (pre-existing expo-router route literal warnings remain unchanged).

Test plan

• Open the host web dashboard for a test event in a browser; have two clients (mobile or curl) join.
• Trigger a connection create — confirm both rows appear live with "1 link" each, no refresh.
• On mobile, mark squares to complete a line — confirm the leaderboard shows "1 line" live and re-sorts.
• Fill the entire grid (blackout) — confirm "completed" checkmark and top-of-board sort.
• Delete the connection from the host side — confirm both rows decrement to 0 links live.