feat(api): add stats chart endpoint for admin access with time series data

feat(dayjs): integrate dayjs for date handling and formatting across the application
refactor(routes): update date handling in id-tags, transactions, users, and dashboard routes to use dayjs
style(globals): improve CSS variable definitions for better readability and consistency
deps: add dayjs as a dependency for date manipulation

apps/web/app/dashboard/charge/page.tsx

@@ -13,6 +13,7 @@ import {
   Xmark,
 } from "@gravity-ui/icons";
 import { api } from "@/lib/api";
+import dayjs from "@/lib/dayjs";
 
 // ── Status maps (same as charge-points page) ────────────────────────────────
 
@@ -411,7 +412,7 @@ export default function ChargePage() {
                 .map((cp) => {
                   const online =
                     !!cp.lastHeartbeatAt &&
-                    Date.now() - new Date(cp.lastHeartbeatAt).getTime() < 120_000;
+                    dayjs().diff(dayjs(cp.lastHeartbeatAt), "second") < 120;
                   const availableCount = cp.connectors.filter(
                     (c) => c.status === "Available",
                   ).length;