ui: undo toast after trash / archive

A global ToastHost (mounted in the app shell) shows a transient toast with
an Undo action, driven by the ui store (showToast/dismiss/runAction, 5s
auto-dismiss). The notes store fires it centrally: trash → Undo restores;
archive → Undo unarchives — so it works from card, editor, and keyboard.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

frontend/src/stores/notes.ts

@@ -1,6 +1,7 @@
 import { defineStore } from "pinia";
 import { ref } from "vue";
 import { api } from "../api/client";
+import { useUiStore } from "./ui";
 import type { NoteColor } from "../notes/colors";
 
 export type NoteView = "active" | "archived" | "trash";
@@ -103,7 +104,10 @@ export const useNotesStore = defineStore("notes", () => {
   }
 
   const setPinned = (id: string, pinned: boolean) => mutate(id, { pinned });
-  const setArchived = (id: string, archived: boolean) => mutate(id, { archived });
+  const setArchived = async (id: string, archived: boolean): Promise<void> => {
+    await mutate(id, { archived });
+    if (archived) useUiStore().showToast("Note archived", "Undo", () => void setArchived(id, false));
+  };
   const setColor = (id: string, color: NoteColor) => mutate(id, { color });
   const setKind = (id: string, kind: NoteKind) => mutate(id, { kind });
   const setReminder = (id: string, remindAt: string | null) => mutate(id, { remind_at: remindAt });
@@ -172,6 +176,7 @@ export const useNotesStore = defineStore("notes", () => {
 
   async function trash(id: string): Promise<void> {
     reconcile(await api.post<Note>(`/api/notes/${id}/trash`));
+    useUiStore().showToast("Note moved to trash", "Undo", () => void restore(id));
   }
 
   async function restore(id: string): Promise<void> {