feat(search): has:image/file/video filters + recent searches

- Add three msgtype toggle chips (Images/Files/Video) to the search filter
  bar, mirroring the existing "Has link" chip. The Matrix search API can't
  filter by msgtype server-side, so results are post-filtered client-side
  (union match on event.content.msgtype, dropping now-empty groups); the
  server request is unchanged. Visible count may be lower than the server
  total — inherent to client-side filtering.
- Recent searches: last 10 distinct terms persisted via a new
  state/recentSearches.ts (atomWithStorage, error-safe, mirrors
  scheduledMessages). Shown as clickable chips when the search input is
  focused + empty, with a Clear affordance; clicking re-runs the search.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/state/recentSearches.ts

@@ -0,0 +1,38 @@
+import { atom } from 'jotai';
+import { atomWithStorage, createJSONStorage } from 'jotai/utils';
+
+const STORAGE_KEY = 'cinny_recent_searches_v1';
+const MAX_RECENT_SEARCHES = 10;
+
+// Internal atom persists as a plain string[] (JSON-serializable).
+const internalAtom = atomWithStorage<string[]>(
+  STORAGE_KEY,
+  [],
+  createJSONStorage(() => localStorage),
+);
+
+/**
+ * Global atom: string[] of the most recent distinct, non-empty search terms.
+ * Most-recent first, deduped, capped at MAX_RECENT_SEARCHES.
+ * Backed by localStorage so recent searches survive page refreshes.
+ */
+export const recentSearchesAtom = atom(
+  (get): string[] => get(internalAtom),
+  (_get, set, updater: string[] | ((prev: string[]) => string[])) => {
+    set(internalAtom, (prev) => {
+      const prevList = Array.isArray(prev) ? prev : [];
+      const next = typeof updater === 'function' ? updater(prevList) : updater;
+      return next;
+    });
+  },
+);
+
+/**
+ * Prepend a search term: dedupes (case-sensitive), drops empties, caps at 10.
+ */
+export const addRecentSearch = (prev: string[], term: string): string[] => {
+  const trimmed = term.trim();
+  if (!trimmed) return prev;
+  const withoutDupe = prev.filter((t) => t !== trimmed);
+  return [trimmed, ...withoutDupe].slice(0, MAX_RECENT_SEARCHES);
+};