feat(social): per-game friend request to disguised robots + lobby/stats/tile cosmetics

Functional: the in-game add-friend handshake aimed at an auto-match opponent who is
secretly a pooled robot now records the request per (game, seat) in a new
robot_friend_requests table -- never against the shared robot account -- mirroring the
robot_blocks pattern. The shared account stays out of friendships, the "requested" state
is pinned to the seat (not leaked across the player's other games), the robot ignores it,
and a background reaper drops the row 7 days after its game finishes. The outgoing-requests
list carries these per-game rows so the seat control stays disabled across reloads. No
withdraw UI, per owner decision.

Cosmetics:
- Lobby: an in-progress game tints the viewer's own score number green when leading or
  tied, red when trailing (reusing --ok/--danger); scores now render in seat-number order,
  matching the over-the-board scoreboard.
- Stats: the per-variant best move is laid out on two lines -- the variant label, then the
  score (right-aligned in its column) and the word tiles (left-aligned) below it.
- Dark theme: the played-tile background is a touch darker so a player-placed tile reads
  with more contrast (light theme unchanged).

Docs (ARCHITECTURE, FUNCTIONAL + _ru mirror, backend README, UI_DESIGN) updated in the
same change.

ui/src/lib/client.ts

@@ -22,6 +22,7 @@ import type {
   LinkResult,
   MatchResult,
   MoveResult,
+  OutgoingList,
   Profile,
   ProfileUpdate,
   PushEvent,
@@ -118,9 +119,12 @@ export interface GatewayClient {
   // --- friends ---
   friendsList(): Promise<AccountRef[]>;
   friendsIncoming(): Promise<AccountRef[]>;
-  /** Addressees the caller has already requested (pending or declined); cannot re-request. */
-  friendsOutgoing(): Promise<AccountRef[]>;
-  friendRequest(accountId: string): Promise<void>;
+  /** Addressees the caller has already requested (pending or declined; cannot re-request),
+   *  plus the per-game disguised-robot requests that keep the in-game 🤝 disabled by seat. */
+  friendsOutgoing(): Promise<OutgoingList>;
+  /** Send a friend request. A non-empty gameId marks an in-game request, so a disguised-robot
+   *  opponent is recorded as a per-game request rather than against the shared robot account. */
+  friendRequest(accountId: string, gameId?: string): Promise<void>;
   friendRespond(requesterId: string, accept: boolean): Promise<void>;
   friendCancel(accountId: string): Promise<void>;
   unfriend(accountId: string): Promise<void>;