feat(enakgame): filter play history by game and status

GET /customer/enakgame/sessions takes optional game_id and status, so a game
reloaded mid-play finds the session it was running (status=STARTED) instead
of starting a new one and charging EnakCoin again. An invalid game_id or
status is refused.

integration-enakgame.md §4.4 now describes recovery after a reload: keep the
session_id in sessionStorage, continue a STARTED session before expires_at,
and call complete again for a COMPLETED one to get the full answer, prize
included. The mobile guide and RFC §11 mention the filters.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/repository/enakgame_repository_test.go

@@ -287,7 +287,7 @@ func TestGameSessionRepository_ReadsAndMoves(t *testing.T) {
 	assert.True(t, got.Flagged)
 	assert.NotNil(t, got.CompletionFailedAt)
 
-	sessions, total, err := f.sessions.ListCustomerSessions(ctx, f.customer, 0, 1)
+	sessions, total, err := f.sessions.ListCustomerSessions(ctx, CustomerSessionFilter{CustomerID: f.customer, Limit: 1})
 	require.NoError(t, err)
 	assert.EqualValues(t, 2, total)
 	assert.Len(t, sessions, 1)