feat: add minimal chart to display API data with hardcoded parameters

server/frontend/public/assets/js/main.js

@@ -0,0 +1,10 @@
+window.onload = loadData
+
+async function loadData() {
+    const points = await fetchConsumption({
+      start: '2026-05-04T00:00:00',
+      end: '2026-05-09T00:00:00',
+      granularity: 'day',
+    });
+    renderChart(points);
+}