feat(stats): best-move word, moves & hint-share, and a hint-count fix (#81)

The statistics screen gains real depth, plus a hint-count bug fix found along the way.

- Best move per variant: the screen shows the actual best-move word (drawn as game
  tiles; a wildcard shows its letter but no value), broken down by game variant, empty
  variants omitted. New account_best_move table, written at game finish.
- Moves & hint share: two new lifetime tiles — the player's play count and the share of
  plays that used a hint — from summed account_stats counters (moves, hints_used).
  Honest-AI games are excluded, like the rest of the stats.
- Hint-count fix: the in-game hint badge no longer goes stale across games. The global
  wallet now rides the wire apart from the per-game allowance (wallet_balance on
  StateView/HintResult/StatsView), so the client reads the live wallet rather than a
  per-game snapshot; game_players.hints_used now counts every hint (allowance + wallet),
  its true per-game total.
- Account merge: sums the new moves/hints_used counters and merges the per-variant best
  moves (higher score kept), which it previously dropped.
- Admin: the user card shows Moves and Hints used.
- UI polish: tab/label wording, game-over text, and e2e selectors hardened against label
  changes.

All wire additions are trailing (backward-compatible). Docs (ARCHITECTURE, FUNCTIONAL +ru,
UISN_DESIGN) updated in step.

ui/src/lib/mock/data.ts

@@ -50,7 +50,47 @@ export const MOCK_FRIENDS: AccountRef[] = [{ accountId: 'kaya', displayName: 'Ka
 
 export const MOCK_INCOMING: AccountRef[] = [{ accountId: 'rick', displayName: 'Rick' }];
 
-export const MOCK_STATS: Stats = { wins: 7, losses: 4, draws: 1, maxGamePoints: 421, maxWordPoints: 95 };
+export const MOCK_STATS: Stats = {
+  wins: 7,
+  losses: 4,
+  draws: 1,
+  maxGamePoints: 421,
+  maxWordPoints: 134,
+  moves: 248, // plays across all games
+  hintsUsed: 12, // -> hint share 12/248 = 4.8%
+  // Letters are lower-cased as the backend emits them; the tile renderer upper-cases for
+  // display. The 'd' in "wonderful" is a blank (value 0) to exercise wildcard rendering.
+  // Erudit is absent on purpose, so the screen demonstrates skipping a not-yet-played variant.
+  bestMoves: [
+    {
+      variant: 'scrabble_en',
+      score: 134,
+      word: [
+        { letter: 'w', value: 4, blank: false },
+        { letter: 'o', value: 1, blank: false },
+        { letter: 'n', value: 1, blank: false },
+        { letter: 'd', value: 0, blank: true },
+        { letter: 'e', value: 1, blank: false },
+        { letter: 'r', value: 1, blank: false },
+        { letter: 'f', value: 4, blank: false },
+        { letter: 'u', value: 1, blank: false },
+        { letter: 'l', value: 1, blank: false },
+      ],
+    },
+    {
+      variant: 'scrabble_ru',
+      score: 88,
+      word: [
+        { letter: 'с', value: 1, blank: false },
+        { letter: 'ъ', value: 10, blank: false },
+        { letter: 'ё', value: 4, blank: false },
+        { letter: 'м', value: 2, blank: false },
+        { letter: 'к', value: 2, blank: false },
+        { letter: 'а', value: 1, blank: false },
+      ],
+    },
+  ],
+};
 
 export function mockInvitations(): Invitation[] {
   return [