Address PR #215 review: temporary notes hardening

Must-fix:
- CHANGELOG: add [Unreleased]/Added entry for temporary notes (#201).
- temporary-note-cleanup: re-check temporary_expires_at at deletion time so a
  concurrent "Make permanent" (sets it NULL) between the batch SELECT and the
  per-row removePage wins the race and the note is not trashed. Add unit tests
  for the make-permanent and already-trashed race windows.

Non-blocking review items:
- temporary-note-cleanup: cap the sweep batch (LIMIT 500) so a large backlog is
  not loaded into memory; remainder drains on the next hourly run.
- client: extract duplicated post-toggle cache sync into
  syncTemporaryExpiresInCache() shared by the header menu and the banner.
- Remove the tautological migration spec that mocked the whole Kysely builder.
- Tests: cover create() frozen temporaryExpiresAt (workspace override + NULL
  default fallback + non-temporary skips lookup) and restorePage disarming the
  timer (temporaryExpiresAt: null).

Deferred (forward-looking, non-blocking): extract
PageService.computeTemporaryExpiresAt() to dedupe the deadline formula and drop
the @InjectKysely from PageTemplateController; replace migration unit test with
a real Postgres up/down integration test.

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

apps/server/src/database/repos/page/page.repo.restore.spec.ts

@@ -0,0 +1,64 @@
+import { PageRepo } from './page.repo';
+
+/**
+ * Regression guard for #201: restorePage must disarm the temporary-note death
+ * timer by setting `temporaryExpiresAt = null` alongside the un-delete fields.
+ * Otherwise a restored note whose frozen deadline already passed would be
+ * re-trashed by the very next cleanup sweep. There is no real DB here — a
+ * chainable Kysely proxy records every `.set(...)` payload so we can assert the
+ * single restore UPDATE clears the deadline.
+ */
+function makeRestoreDbStub(opts: {
+  pageToRestore: any;
+  descendants: any[];
+}) {
+  const setCalls: any[] = [];
+  const proxy: any = new Proxy(function () {}, {
+    get(_t, prop) {
+      if (prop === 'then') return undefined;
+      if (prop === 'set')
+        return (payload: any) => {
+          setCalls.push(payload);
+          return proxy;
+        };
+      if (prop === 'executeTakeFirst')
+        return () => Promise.resolve(opts.pageToRestore);
+      if (prop === 'execute') return () => Promise.resolve(opts.descendants);
+      if (prop === 'withRecursive')
+        return (_name: string, cb: any) => {
+          // Exercise the recursive CTE builder against the proxy without a DB.
+          try {
+            cb(proxy);
+          } catch {
+            // builder shape only; ignore
+          }
+          return proxy;
+        };
+      return () => proxy;
+    },
+  });
+  return { proxy, setCalls };
+}
+
+describe('PageRepo.restorePage temporary-timer disarm (#201)', () => {
+  it('clears temporaryExpiresAt together with the un-delete fields', async () => {
+    const { proxy, setCalls } = makeRestoreDbStub({
+      // No parent => the deleted-parent lookup and detach branch are skipped, so
+      // the only UPDATE is the bulk restore we assert on.
+      pageToRestore: { id: 'p1', parentPageId: null, spaceId: 's1' },
+      descendants: [{ id: 'p1' }],
+    });
+    const eventEmitter = { emit: jest.fn() } as any;
+
+    const repo = new PageRepo(proxy, {} as any, eventEmitter);
+
+    await repo.restorePage('p1', 'w1');
+
+    expect(setCalls).toHaveLength(1);
+    expect(setCalls[0]).toEqual({
+      deletedById: null,
+      deletedAt: null,
+      temporaryExpiresAt: null,
+    });
+  });
+});