feat(admin): add the admin users page and view as

src/hooks/useCurrentUser.js

@@ -0,0 +1,34 @@
+import {useEffect, useState} from 'react';
+import {apiFetch} from '../utils/api.js';
+import {sessionStamp} from '../utils/auth.js';
+
+/**
+ * The stored role and the active role ("view as") of the logged-in user, or null while loading and on any error.
+ * Loads again after a new login or a role switch (see sessionStamp) on the next render.
+ */
+export default function useCurrentUser(enabled) {
+    const [user, setUser] = useState(null);
+    const stamp = sessionStamp();
+
+    useEffect(() => {
+        if (!enabled || !stamp) {
+            setUser(null);
+            return undefined;
+        }
+        let cancelled = false;
+        (async () => {
+            try {
+                const response = await apiFetch(`${import.meta.env.VITE_API_URL}/api/users/me?v=1`);
+                const data = response.ok ? await response.json() : null;
+                if (!cancelled) setUser(data && {role: data.role, activeRole: data.activeRole ?? data.role});
+            } catch {
+                if (!cancelled) setUser(null);
+            }
+        })();
+        return () => {
+            cancelled = true;
+        };
+    }, [enabled, stamp]);
+
+    return user;
+}