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.

docs/UI_DESIGN.md

@@ -279,9 +279,16 @@ enabled on the first, uncached load) and flip in place when an event refreshes t
   and the "searching" hint is hidden; the game starts already seated, the opponent shows as **🤖**
   everywhere (score card, lobby row, turn line), the add-friend 🤝 is never drawn, and the chat's
   send field and 🛎️ nudge stay **disabled** while the 🔎 dictionary word-check keeps working.
-- **Statistics** (`screens/Stats.svelte`, the lobby 📊 tab): a 2-column grid of stat
-  cards (wins / losses / draws / games / win-rate / best game / best move) — pure
-  numbers, no charts.
+- **Statistics** (`screens/Stats.svelte`, the lobby ✏️ tab): a 2-column grid of stat
+  cards (games / wins / draws / losses / moves / hint-share / best game / win-rate) —
+  pure numbers, no charts; hint-share is a one-decimal percentage in the active locale's
+  notation (e.g. "4.8%" / "4,8%") — followed by a **full-width "best move" card** that
+  breaks the best move
+  down per variant: one row per played variant (catalogue order, empty variants
+  omitted) with the variant name on the left, the **word drawn as game tiles**
+  (`components/WordTiles.svelte`, the board's placed-tile look at a small fixed size;
+  a wildcard shows its letter but no value) right-aligned to a shared edge, and the
+  score right-aligned in its own column.
 - **Profile editing** (`screens/Profile.svelte`): an inline form — display name, a
   **UTC-offset** timezone dropdown (defaulting to the browser's offset), the away
   window as hour + 10-minute dropdowns (24-hour, ≤ 12 h), and block toggles — plus an