feat(frontend): add API client, layout, and routing

- Create Axios-based API client with sources, jobs, and dashboard endpoints
- Add responsive Layout component with navigation sidebar
- Set up React Router with Dashboard, Backups, and Settings routes
- Configure TanStack Query provider with default options
- Use lucide-react for navigation icons

frontend/node_modules/d3-time/src/day.js

@@ -0,0 +1,35 @@
+import {timeInterval} from "./interval.js";
+import {durationDay, durationMinute} from "./duration.js";
+
+export const timeDay = timeInterval(
+  date => date.setHours(0, 0, 0, 0),
+  (date, step) => date.setDate(date.getDate() + step),
+  (start, end) => (end - start - (end.getTimezoneOffset() - start.getTimezoneOffset()) * durationMinute) / durationDay,
+  date => date.getDate() - 1
+);
+
+export const timeDays = timeDay.range;
+
+export const utcDay = timeInterval((date) => {
+  date.setUTCHours(0, 0, 0, 0);
+}, (date, step) => {
+  date.setUTCDate(date.getUTCDate() + step);
+}, (start, end) => {
+  return (end - start) / durationDay;
+}, (date) => {
+  return date.getUTCDate() - 1;
+});
+
+export const utcDays = utcDay.range;
+
+export const unixDay = timeInterval((date) => {
+  date.setUTCHours(0, 0, 0, 0);
+}, (date, step) => {
+  date.setUTCDate(date.getUTCDate() + step);
+}, (start, end) => {
+  return (end - start) / durationDay;
+}, (date) => {
+  return Math.floor(date / durationDay);
+});
+
+export const unixDays = unixDay.range;