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/components/WordTiles.svelte

@@ -0,0 +1,53 @@
+<script lang="ts">
+  // A best-move word drawn as a row of game tiles, mirroring the board's placed-tile
+  // look (letter top-left, point value bottom-right) at a small fixed size. A blank tile
+  // shows its letter but no value, exactly as on the board. Letters are upper-cased for
+  // display. The tile values ride on each tile, so this renders without the variant's
+  // alphabet table (which the statistics screen has not cached).
+  import type { BestMoveTile } from '../lib/model';
+
+  let { word }: { word: BestMoveTile[] } = $props();
+
+  const label = $derived(word.map((t) => t.letter).join('').toUpperCase());
+</script>
+
+<span class="word" aria-label={label}>
+  {#each word as tile, i (i)}
+    <span class="tile" class:blank={tile.blank} aria-hidden="true">
+      <span class="letter">{tile.letter.toUpperCase()}</span>
+      {#if !tile.blank}<span class="val">{tile.value}</span>{/if}
+    </span>
+  {/each}
+</span>
+
+<style>
+  .word {
+    display: inline-flex;
+    gap: 2px;
+  }
+  .tile {
+    position: relative;
+    flex: none;
+    width: 22px;
+    height: 22px;
+    background: var(--tile-bg);
+    color: var(--tile-text);
+    border-radius: 3px;
+    box-shadow: inset 0 -2px 0 var(--tile-edge);
+  }
+  .letter {
+    position: absolute;
+    top: 6%;
+    left: 11%;
+    font-size: 12px;
+    font-weight: 700;
+    line-height: 1;
+  }
+  .val {
+    position: absolute;
+    right: 8%;
+    bottom: 3%;
+    font-size: 7px;
+    font-weight: 600;
+  }
+</style>