feat: add daily cron scheduler for price checks

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/scheduler.js

@@ -0,0 +1,10 @@
+const cronDefault = require('node-cron');
+
+const SCHEDULE = '0 8 * * *';
+const TIMEZONE = 'Europe/Amsterdam';
+
+function start(runCheck, { cron = cronDefault } = {}) {
+  return cron.schedule(SCHEDULE, runCheck, { timezone: TIMEZONE });
+}
+
+module.exports = { start, SCHEDULE, TIMEZONE };

test/scheduler.test.js

@@ -0,0 +1,21 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+const { start, SCHEDULE, TIMEZONE } = require('../src/scheduler');
+
+test('start schedules the daily check with the expected cron expression and timezone', () => {
+  const calls = [];
+  const fakeCron = {
+    schedule: (expression, fn, options) => {
+      calls.push({ expression, fn, options });
+      return { stop: () => {} };
+    },
+  };
+  const runCheck = async () => {};
+  start(runCheck, { cron: fakeCron });
+  assert.equal(calls.length, 1);
+  assert.equal(calls[0].expression, SCHEDULE);
+  assert.equal(SCHEDULE, '0 8 * * *');
+  assert.equal(calls[0].options.timezone, TIMEZONE);
+  assert.equal(TIMEZONE, 'Europe/Amsterdam');
+  assert.equal(calls[0].fn, runCheck);
+});