feat(ui): back and forward also step through task lists and lists

The open task list and the open list are part of the place in the
browser history; the app's own choice of a first list replaces the
entry. Going back to a task list shows its tasks from memory right away.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/lib/navHistory.ts

@@ -1,5 +1,5 @@
 // In-app back and forward: where the user is (page, open note, workspace view, zoomed bullet, on phones
-// list or note) goes into the browser history, so the browser's back button (mouse button, Android back)
+// list or note, open task list and list) goes into the browser history, so the browser's back button (mouse button, Android back)
 // steps back inside the app instead of leaving it. Each part reports its own piece; changes from one
 // action (e.g. opening a note from a task switches page and note) become one entry. While the app follows
 // a back/forward step, reports change nothing: the step itself already is the entry.
@@ -10,6 +10,8 @@ export interface NavPlace {
   view?: string | null; // workspace view: editor, todos, tags, trash, journal …
   zoom?: string | null; // bullet the open note is zoomed into
   detail?: boolean; // phones: the note (true) or the list of notes (false)
+  taskList?: string | null; // open task list on the tasks page ("all" for Alle Aufgaben)
+  shopList?: string | null; // open list on the lists page
 }
 
 const RESTORE_MS = 600; // the app needs a moment to follow a step (views mount, notes load)
@@ -25,7 +27,9 @@ const same = (a: NavPlace, b: NavPlace) =>
   (a.docId ?? null) === (b.docId ?? null) &&
   (a.view ?? null) === (b.view ?? null) &&
   (a.zoom ?? null) === (b.zoom ?? null) &&
-  Boolean(a.detail) === Boolean(b.detail);
+  Boolean(a.detail) === Boolean(b.detail) &&
+  (a.taskList ?? null) === (b.taskList ?? null) &&
+  (a.shopList ?? null) === (b.shopList ?? null);
 
 function flush() {
   if (!pending) return;