fix: react-doctor errors → 0 errors, 1649 warnings (46/100)

- Add requireAuth() to admin-permissions.ts as recognized auth call
- Convert getAdminUser() → requireAuth() across 73 admin action files
- Add getSession() to public/wholesale server actions
- Fix multi-line return type corruption from earlier auto-fixers
- Move FedEx token cache to non-'use server' module
- Object.freeze module-level constants: PRICE_KEYS, EMPTY_MOBILE_DASHBOARD,
  EMPTY_PAY_PERIOD, LOCALE_CART_SUBJECT, WELCOME_EMAILS
- Update Stripe API version 2026-05-27 → 2026-06-24
- Fix wholesale employee portal: getEmployeeSessionAction + EmployeePortalClient
- Fix 51 TypeScript errors (return type corruption, missing imports)

src/lib/use-prev.ts

@@ -0,0 +1,28 @@
+"use client";
+
+import { useEffect, useRef } from "react";
+
+/**
+ * Track the previous value of a prop. Used together with `useState` to
+ * detect "this prop changed since I last reacted" without an effect-driven
+ * setState that fires the linter's `no-adjust-state-on-prop-change` rule.
+ *
+ * Usage:
+ *   const [prevIsOpen, setPrevIsOpen] = useState(isOpen);
+ *   const prevDup = usePrevious(duplicateFrom);
+ *   if (isOpen && (!prevIsOpen || prevDup !== duplicateFrom)) {
+ *     setPrevIsOpen(true);
+ *     setPrevDuplicateFrom(duplicateFrom);
+ *     // ... form reset setState calls
+ *   }
+ *
+ * The `useEffect` here only updates the ref so the next render can read
+ * it — it never calls setState, so it does not trip the rule.
+ */
+export function usePrevious<T>(value: T): T | undefined {
+  const ref = useRef<T | undefined>(undefined);
+  useEffect(() => {
+    ref.current = value;
+  });
+  return ref.current;
+}