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/gen/fbs/scrabblefb/best-move-view.ts

@@ -0,0 +1,88 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+
+import * as flatbuffers from 'flatbuffers';
+
+import { BestMoveTile } from '../scrabblefb/best-move-tile.js';
+
+
+export class BestMoveView {
+  bb: flatbuffers.ByteBuffer|null = null;
+  bb_pos = 0;
+  __init(i:number, bb:flatbuffers.ByteBuffer):BestMoveView {
+  this.bb_pos = i;
+  this.bb = bb;
+  return this;
+}
+
+static getRootAsBestMoveView(bb:flatbuffers.ByteBuffer, obj?:BestMoveView):BestMoveView {
+  return (obj || new BestMoveView()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+static getSizePrefixedRootAsBestMoveView(bb:flatbuffers.ByteBuffer, obj?:BestMoveView):BestMoveView {
+  bb.setPosition(bb.position() + flatbuffers.SIZE_PREFIX_LENGTH);
+  return (obj || new BestMoveView()).__init(bb.readInt32(bb.position()) + bb.position(), bb);
+}
+
+variant():string|null
+variant(optionalEncoding:flatbuffers.Encoding):string|Uint8Array|null
+variant(optionalEncoding?:any):string|Uint8Array|null {
+  const offset = this.bb!.__offset(this.bb_pos, 4);
+  return offset ? this.bb!.__string(this.bb_pos + offset, optionalEncoding) : null;
+}
+
+score():number {
+  const offset = this.bb!.__offset(this.bb_pos, 6);
+  return offset ? this.bb!.readInt32(this.bb_pos + offset) : 0;
+}
+
+word(index: number, obj?:BestMoveTile):BestMoveTile|null {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? (obj || new BestMoveTile()).__init(this.bb!.__indirect(this.bb!.__vector(this.bb_pos + offset) + index * 4), this.bb!) : null;
+}
+
+wordLength():number {
+  const offset = this.bb!.__offset(this.bb_pos, 8);
+  return offset ? this.bb!.__vector_len(this.bb_pos + offset) : 0;
+}
+
+static startBestMoveView(builder:flatbuffers.Builder) {
+  builder.startObject(3);
+}
+
+static addVariant(builder:flatbuffers.Builder, variantOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(0, variantOffset, 0);
+}
+
+static addScore(builder:flatbuffers.Builder, score:number) {
+  builder.addFieldInt32(1, score, 0);
+}
+
+static addWord(builder:flatbuffers.Builder, wordOffset:flatbuffers.Offset) {
+  builder.addFieldOffset(2, wordOffset, 0);
+}
+
+static createWordVector(builder:flatbuffers.Builder, data:flatbuffers.Offset[]):flatbuffers.Offset {
+  builder.startVector(4, data.length, 4);
+  for (let i = data.length - 1; i >= 0; i--) {
+    builder.addOffset(data[i]!);
+  }
+  return builder.endVector();
+}
+
+static startWordVector(builder:flatbuffers.Builder, numElems:number) {
+  builder.startVector(4, numElems, 4);
+}
+
+static endBestMoveView(builder:flatbuffers.Builder):flatbuffers.Offset {
+  const offset = builder.endObject();
+  return offset;
+}
+
+static createBestMoveView(builder:flatbuffers.Builder, variantOffset:flatbuffers.Offset, score:number, wordOffset:flatbuffers.Offset):flatbuffers.Offset {
+  BestMoveView.startBestMoveView(builder);
+  BestMoveView.addVariant(builder, variantOffset);
+  BestMoveView.addScore(builder, score);
+  BestMoveView.addWord(builder, wordOffset);
+  return BestMoveView.endBestMoveView(builder);
+}
+}