feat(offline): per-seat medals in local games; drop the you-won text + lobby medal

For a local (offline) game the outcome is not always about a single
'you' (hotseat is 2-4 players), so:
- Game.svelte: a finished local game no longer shows the viewer-centric
  'you won/lost/draw' status; instead each seat plaque shows a per-seat
  place medal, left of the name (result.seatMedal — trophy for the winner,
  then places by score; a draw medals everyone).
- Lobby.svelte: a local game shows no lobby medal (resultBadge is
  viewer-centric and no seat matches the account) — its result lives on
  the in-game plaques.
- result.ts: seatMedal(game, seat), unit-tested.

ui/src/screens/Lobby.svelte

@@ -353,9 +353,11 @@
                           >{/each}</span
                       >
                     </span>
-                    <!-- Re-key on the per-card blink nonce so a repeat blink restarts the fade. -->
+                    <!-- Re-key on the per-card blink nonce so a repeat blink restarts the fade. A
+                         local (offline) game shows no lobby medal — its result lives on the in-game
+                         seat plaques, and resultBadge is viewer-centric (no seat matches the account). -->
                     {#key blinkNonce.get(g.id) ?? 0}
-                      <span class="emoji" class:blink={blinkingIds.has(g.id)}>{resultBadge(g, myId).emoji}</span>
+                      <span class="emoji" class:blink={blinkingIds.has(g.id)}>{isLocalGameId(g.id) ? '' : resultBadge(g, myId).emoji}</span>
                     {/key}
                   </button>
                   {#if group.finished || g.hotseat}