feat(ui): tile-crossword loading splash for cold lobby open

On a cold app open the lobby's game list arrives over the network; on a
slow link the empty "no games yet" line flashed before the games loaded.
Add a full-screen tile splash that lays a Scrabble crossword of ЭРУДИТ /
ЗАГРУЗКА / ОЖИДАНИЕ (Эрудит point values, hardcoded since the alphabet
table is not cached at boot) until the lobby's first load settles, then
removes itself to reveal the populated list.

- lib/splash.ts: pure layout + reveal schedule (unit-tested).
- components/Splash.svelte: App-level overlay; per-tile drop-in; loops
  ЗАГРУЗКА → ОЖИДАНИЕ until ready, dismisses on a word boundary. Static
  ЭРУДИТ under reduced motion / the mock build.
- app state: lobbyReady (set by Lobby on first settle) + splashDone,
  reset on logout.
- App.svelte: overlay while routeIsLobby && !splashDone; the plain text
  splash now only covers non-lobby deep-links during bootstrap.
- docs: UI_DESIGN + FUNCTIONAL (+ _ru).

docs/FUNCTIONAL.md

@@ -65,6 +65,10 @@ account is kept and the guest's games move into it. A merge is blocked only whil
 two accounts share a game still in progress.
 
 ### Lobby & matchmaking
+On a cold open the lobby greets the player with a brief **loading splash** — Scrabble tiles
+spelling **ЭРУДИТ / ЗАГРУЗКА / ОЖИДАНИЕ** as a small crossword — that clears the moment the
+games list is ready, so the list never flashes an "empty" state on a slow connection.
+
 The lobby lists **my games** and offers a bottom tab bar — new game, statistics, and a
 **⚙️ settings** tab opening the settings hub (settings, profile, friends, about). The
 **my games** list groups games into three