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/codec.test.ts

@@ -284,6 +284,8 @@ describe('codec', () => {
     fb.StatsView.addDraws(b, 1);
     fb.StatsView.addMaxGamePoints(b, 420);
     fb.StatsView.addMaxWordPoints(b, 90);
+    fb.StatsView.addMoves(b, 248);
+    fb.StatsView.addHintsUsed(b, 12);
     b.finish(fb.StatsView.endStatsView(b));
     expect(decodeStats(b.asUint8Array())).toEqual({
       wins: 7,
@@ -291,6 +293,57 @@ describe('codec', () => {
       draws: 1,
       maxGamePoints: 420,
       maxWordPoints: 90,
+      moves: 248,
+      hintsUsed: 12,
+      bestMoves: [],
+    });
+  });
+
+  it('decodes a StatsView carrying a per-variant best move with a blank tile', () => {
+    const b = new Builder(256);
+    // Word "ca" where the 'a' is a blank: it carries its letter but scores 0.
+    const cLetter = b.createString('c');
+    fb.BestMoveTile.startBestMoveTile(b);
+    fb.BestMoveTile.addLetter(b, cLetter);
+    fb.BestMoveTile.addValue(b, 3);
+    fb.BestMoveTile.addBlank(b, false);
+    const tileC = fb.BestMoveTile.endBestMoveTile(b);
+    const aLetter = b.createString('a');
+    fb.BestMoveTile.startBestMoveTile(b);
+    fb.BestMoveTile.addLetter(b, aLetter);
+    fb.BestMoveTile.addValue(b, 0);
+    fb.BestMoveTile.addBlank(b, true);
+    const tileA = fb.BestMoveTile.endBestMoveTile(b);
+    const word = fb.BestMoveView.createWordVector(b, [tileC, tileA]);
+    const variant = b.createString('scrabble_en');
+    fb.BestMoveView.startBestMoveView(b);
+    fb.BestMoveView.addVariant(b, variant);
+    fb.BestMoveView.addScore(b, 90);
+    fb.BestMoveView.addWord(b, word);
+    const bm = fb.BestMoveView.endBestMoveView(b);
+    const bestMoves = fb.StatsView.createBestMovesVector(b, [bm]);
+    fb.StatsView.startStatsView(b);
+    fb.StatsView.addWins(b, 7);
+    fb.StatsView.addBestMoves(b, bestMoves);
+    b.finish(fb.StatsView.endStatsView(b));
+    expect(decodeStats(b.asUint8Array())).toEqual({
+      wins: 7,
+      losses: 0,
+      draws: 0,
+      maxGamePoints: 0,
+      maxWordPoints: 0,
+      moves: 0,
+      hintsUsed: 0,
+      bestMoves: [
+        {
+          variant: 'scrabble_en',
+          score: 90,
+          word: [
+            { letter: 'c', value: 3, blank: false },
+            { letter: 'a', value: 0, blank: true },
+          ],
+        },
+      ],
     });
   });