phase-1: optimize code

ui/src/routes/calls/+page.js

@@ -0,0 +1,8 @@
+export async function load({ fetch }) {
+  const [callsRes, calRes] = await Promise.all([fetch('/api/calls'), fetch('/api/calls/calendar')]);
+
+  const { calls } = callsRes.ok ? await callsRes.json() : { calls: [] };
+  const { events } = calRes.ok ? await calRes.json() : { events: [] };
+
+  return { calls, events };
+}