feat(stats): per-game hints used + lifetime moves and hint share

Store the hints a player used in each game, and add two lifetime tiles —
Moves and Hint share — to the statistics screen.

- per-game: game_players.hints_used now counts EVERY hint (allowance + wallet),
  not just the free allowance, so it is the seat's true total hints used this
  game. The allowance decision (used < HintsPerPlayer) and the hint badge values
  (hints_remaining / wallet_balance) are unchanged — the lobby hint-count fix does
  NOT regress; only the admin "hints used" column, which silently under-counted
  wallet hints, becomes accurate.
- account_stats gains two summed counters: moves (the player's plays — passes and
  exchanges excluded) and hints_used (every hint). Computed at game finish in
  buildStats over the same non-guest, non-honest-AI games as the rest of the stats.
- wire: StatsView gains moves + hints_used (trailing); gateway + UI codec + model;
  regen.
- ui: two tiles (Moves, Hint share = hints_used/moves, one-decimal % in the active
  locale); card order games·wins·draws·losses·moves·hint-share·best game·win-rate.
- docs: ARCHITECTURE §9 + baseline comment, FUNCTIONAL (+ru), UI_DESIGN.

Tests: TestHintPolicy (hints_used counts the wallet hint), TestGameLifecycleAndStats
(moves>0, hints=0), gateway stats round-trip, UI hintShare unit + codec + e2e.

docs/UI_DESIGN.md

@@ -280,8 +280,10 @@ enabled on the first, uncached load) and flip in place when an event refreshes t
   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) — pure numbers, no
-  charts — followed by a **full-width "best move" card** that breaks the best move
+  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;