feat(wasm): playable browser game at /play

Add `SolitaireGame` WASM binding to `solitaire_wasm` exposing draw(),
move_cards(), undo(), auto_complete_step(), and state() — all backed by
the real solitaire_core rules engine.

Add /play route to solitaire_server serving a full vanilla-JS
interactive Klondike game (game.html / game.css / game.js). Features:
drag-and-drop card moves (mouse + touch via PointerEvents), click stock
to draw, double-click card to auto-move to foundation, undo, draw-1/3
toggle, new game, auto-complete animation, win overlay, seed display.
Rebuild solitaire_wasm.js + solitaire_wasm_bg.wasm.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

solitaire_server/src/lib.rs

@@ -205,6 +205,10 @@ fn build_router_inner(state: AppState, rate_limit: bool) -> Router {
             "/replays/{id}",
             get(|| async { Html(include_str!("../web/index.html")) }),
         )
+        .route(
+            "/play",
+            get(|| async { Html(include_str!("../web/game.html")) }),
+        )
         .nest_service("/web", ServeDir::new("solitaire_server/web"));
 
     Router::new()