fix: a new view opens at its top instead of the last view's scroll offset

The router had no scrollBehavior, so Settings entered from a scrolled feed
opened scrolled too, its heading and tab strip under the nav. Back/forward
restores the saved position, and a new query on the same view keeps its
place.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR

frontend/src/router.js

@@ -94,9 +94,25 @@ const routes = [
 const history =
   typeof window !== 'undefined' ? createWebHistory() : createMemoryHistory()
 
+// Where the window lands after a navigation. Without this the router keeps the
+// window's scroll offset, so a view entered from halfway down another one opened
+// halfway down itself, its heading and tab strip under the nav (operator-flagged
+// 2026-09-24, Settings entered from a scrolled feed).
+//   - back/forward returns to where that entry was left;
+//   - the SAME view with a new query (a gallery filter, a Browse or
+//     Subscriptions tab) keeps its place — that is not a new page;
+//   - a new view opens at its top.
+export function scrollBehavior(to, from, savedPosition) {
+  if (savedPosition) return savedPosition
+  if (from.matched.length && to.path === from.path) return false
+  if (to.hash) return { el: to.hash }
+  return { top: 0 }
+}
+
 const router = createRouter({
   history,
-  routes
+  routes,
+  scrollBehavior
 })
 
 const DEFAULT_TITLE = 'FabledCurator'