feat(page): temporary notes — auto-trash after X hours unless made permanent (#201)

"Temporary notes" with a death timer: created via a dedicated hourglass button
in the space-tree header, a note auto-moves to Trash after a configurable X
hours (default 24) unless explicitly made permanent ("structure or die").

Reuses existing mechanisms, mirroring is_template and the trash-cleanup job:
- New nullable column pages.temporary_expires_at (NULL = permanent; non-NULL =
  frozen deadline) + partial index for the sweep; workspace column
  temporary_note_hours (default via DEFAULT_TEMPORARY_NOTE_HOURS = 24).
- create-page DTO `temporary` flag; the deadline is frozen at creation so later
  setting changes never reschedule existing notes.
- POST /pages/toggle-temporary (mirror of toggle-template): arm/clear the timer,
  CASL-guarded via validateCanEdit, cross-workspace NotFound defense-in-depth.
- TemporaryNoteCleanupService: hourly @Interval sweep that soft-deletes expired
  notes through the exact PageRepo.removePage path (recursive over children,
  emits PAGE_SOFT_DELETED), attributed to the creator; idempotent via
  deletedAt IS NULL filters.
- restorePage clears temporary_expires_at so a restored note can't be re-trashed.
- Workspace setting temporary_note_hours (audit-tracked) + a hours editor in
  workspace General settings.
- Client: second create button, orange tree icon, tree + page-header menu toggle
  ("Make temporary"/"Make permanent"), an open-note banner with a rescue action,
  and en/ru i18n.

Tests (unit): toggle-temporary controller (toggle/explicit/permission/cross-ws +
DTO validation), cleanup-job sweep (selection filters, per-note removePage,
error isolation), and a migration up/down sanity. Server tsc, client tsc -b,
and the page+workspace jest suites are green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/src/features/space/components/sidebar/space-sidebar.tsx

@@ -13,6 +13,7 @@ import {
   IconEye,
   IconEyeOff,
   IconFileExport,
+  IconHourglass,
   IconPlus,
   IconSettings,
   IconStar,
@@ -71,6 +72,10 @@ export function SpaceSidebar() {
     handleCreate(null);
   }
 
+  function handleCreateTemporaryPage() {
+    handleCreate(null, { temporary: true });
+  }
+
   return (
     <>
       <div className={classes.navbar}>
@@ -111,16 +116,39 @@ export function SpaceSidebar() {
                 SpaceCaslAction.Manage,
                 SpaceCaslSubject.Page,
               ) && (
-                <Tooltip label={t("Create page")} withArrow position="right">
-                  <ActionIcon
-                    variant="default"
-                    size={18}
-                    onClick={handleCreatePage}
-                    aria-label={t("Create page")}
+                <>
+                  <Tooltip
+                    label={t("Create page")}
+                    withArrow
+                    position="right"
                   >
-                    <IconPlus />
-                  </ActionIcon>
-                </Tooltip>
+                    <ActionIcon
+                      variant="default"
+                      size={18}
+                      onClick={handleCreatePage}
+                      aria-label={t("Create page")}
+                    >
+                      <IconPlus />
+                    </ActionIcon>
+                  </Tooltip>
+
+                  {/* Standalone second button: a "temporary note" auto-moves to
+                      trash after the workspace lifetime unless made permanent. */}
+                  <Tooltip
+                    label={t("New temporary note")}
+                    withArrow
+                    position="right"
+                  >
+                    <ActionIcon
+                      variant="default"
+                      size={18}
+                      onClick={handleCreateTemporaryPage}
+                      aria-label={t("New temporary note")}
+                    >
+                      <IconHourglass />
+                    </ActionIcon>
+                  </Tooltip>
+                </>
               )}
             </Group>
           </Group>