Home money counts: billing-stats reads Billing through the client's api object (the module root has no stats(); the home showed the tiles empty) (#186)

ddiff --git a/server/monetization/billing-stats.js b/server/monetization/billing-stats.js
iindex 65cbcb11..ec1c7870 100644
---- a/server/monetization/billing-stats.js
++++ b/server/monetization/billing-stats.js
@@@ -10,7 +10,7 @@
   * One Billing read serves both, cached five minutes (a failure is cached for a minute and answers null: the board
   * shows the tiles empty rather than a guess).
   */
--const api = require('./billing-client');
++const { api } = require('./billing-client');
  
  const TTL_MS = 5 * 60_000;
  const MISS_MS = 60_000;
ddiff --git a/test/billing-stats.test.js b/test/billing-stats.test.js
iindex 28352c5b..31914a5e 100644
---- a/test/billing-stats.test.js
++++ b/test/billing-stats.test.js
@@@ -9,7 +9,7 @@
  const assert = require('assert');
  
  (async () => {
--    const api = require('../server/monetization/billing-client');
++    const { api } = require('../server/monetization/billing-client');   // the module's api object, as billing-stats.js uses it
      let calls = 0;
      let fail = false;
      const days = Array.from({ length: 90 }, (_, i) => ({ day: new Date(Date.now() - (89 - i) * 86400000).toISOString().slice(0, 10), value: i === 89 ? 500 : (i === 88 ? 250 : 0) }));