Add user purchase statistics tab

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

frontend/src/features/stats/UserStats.tsx

@@ -0,0 +1,55 @@
+import { useQuery } from "@apollo/client";
+import { ResponsiveBar } from "@nivo/bar";
+import React from "react";
+
+import { GQLError } from "../../components/GQLError";
+import { UserStatsDocument } from "../../types";
+import styles from "./Stats.module.css";
+import { StatsView } from "./StatsView";
+import { chartTheme } from "./chartTheme";
+
+const UserStats = () => {
+  const { data, loading, error } = useQuery(UserStatsDocument);
+
+  if (error) return <GQLError error={error} />;
+
+  const users = (data?.allUsers || [])
+    .filter((user) => Number(user.profile?.orderSumTotal || 0) > 0)
+    .map((user) => ({
+      name: `${user.firstName}${user.lastName ? ` ${user.lastName[0]}.` : ""}`,
+      total: Number(user.profile?.orderSumTotal || 0),
+    }))
+    .sort((a, b) => b.total - a.total)
+    .slice(0, 10);
+
+  return (
+    <StatsView loading={loading}>
+      <h3>Topp 10 etter total kjøpesum</h3>
+      {users.length ? (
+        <div className={styles.chart} style={{ height: Math.max(320, users.length * 44) }}>
+          <ResponsiveBar
+            data={users}
+            keys={["total"]}
+            indexBy="name"
+            layout="horizontal"
+            theme={chartTheme}
+            margin={{ top: 10, right: 35, bottom: 40, left: 100 }}
+            padding={0.3}
+            enableLabel={false}
+            axisBottom={{
+              legend: "Kjøp totalt (kr)",
+              legendPosition: "middle",
+              legendOffset: 32,
+            }}
+            axisLeft={null}
+            valueFormat={(value) => `${Number(value).toLocaleString("no")} kr`}
+          />
+        </div>
+      ) : (
+        <p>Ingen kjøp å vise ennå.</p>
+      )}
+    </StatsView>
+  );
+};
+
+export default UserStats;