Fix quote/job create page jumping to bottom on fresh load

The wizard scroll-restore saved scroll position on form submit but never
cleared it if the server redirected to a success page. Next fresh visit
to the same URL found the stale sessionStorage key and jumped down.

Fix: track whether the page unload was caused by our own form submit.
On pagehide for any other reason (nav link, success redirect), remove
the key so it never fires on a clean page load.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/wwwroot/js/item-wizard.js

@@ -91,13 +91,23 @@ document.addEventListener('DOMContentLoaded', () => {
         ownerForm.addEventListener('submit', writeHiddenFields, { capture: true });
 
         // Save scroll position before the form causes a full-page reload so we can
-        // restore it after the server redirects back to this page. Key is path-specific
-        // so navigating away and back doesn't restore a stale position.
+        // restore it after the server redirects back to this page on a validation error.
+        // Key is path-specific; cleared on pagehide unless we're leaving via a submit so
+        // a fresh navigation to this page never restores a stale position.
         const scrollKey = 'wizardScrollY:' + location.pathname;
+        let wizardSubmitting = false;
         ownerForm.addEventListener('submit', () => {
+            wizardSubmitting = true;
             sessionStorage.setItem(scrollKey, String(Math.round(window.scrollY)));
         }, { capture: true });
 
+        // If the page unloads for any reason other than our own form submit (e.g. the
+        // user clicks a nav link or the server redirects to a success page), discard the
+        // saved position so it doesn't fire on the next fresh visit.
+        window.addEventListener('pagehide', () => {
+            if (!wizardSubmitting) sessionStorage.removeItem(scrollKey);
+        });
+
         // Restore on load — fire after layout is painted so scrollTo lands correctly.
         const savedY = sessionStorage.getItem(scrollKey);
         if (savedY !== null) {