Serve practice mode from the main server, add mode switch, fix touch

Practice mode is now at /practice on server.py instead of a separate
server, with a button in the bottom-right corner of each page to the
other mode. Touch: no double-tap zoom, no sticky hover after a tap, no
long-press selection on the board, and a pressed look on tapped squares.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

server.py

@@ -17,6 +17,7 @@ from pathlib import Path
 
 from aiohttp import WSMsgType, web
 
+import practice
 from game import Game
 
 STATIC_DIR = Path(__file__).parent / "static"
@@ -122,6 +123,10 @@ async def index(request):
     return web.FileResponse(STATIC_DIR / "index.html")
 
 
+async def practice_page(request):
+    return web.FileResponse(STATIC_DIR / "practice.html")
+
+
 async def game_socket(request):
     code = normalize_code(request.query.get("game", ""))
     ws = web.WebSocketResponse(max_msg_size=MAX_MESSAGE_SIZE)
@@ -229,6 +234,8 @@ def make_app():
     app = web.Application(middlewares=[no_cache])
     app.router.add_get("/", index)
     app.router.add_get("/ws", game_socket)
+    app.router.add_get("/practice", practice_page)
+    app.router.add_post("/api/play", practice.play)
     app.router.add_static("/static", STATIC_DIR)
     app.cleanup_ctx.append(start_reaper)
     return app