fix(search): apply the date range to server results client-side

from_ts/to_ts are not Matrix filter fields; the server dropped them, so
the range only worked for the local encrypted-room search. Stop sending
them and post-filter server results by origin_server_ts with the same
inclusive predicate. Unit-tested; docs corrected.

Fixes #13

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/features/message-search/MessageSearch.tsx

@@ -36,6 +36,7 @@ import { mDirectAtom } from '../../state/mDirectList';
 import { getStateEvent } from '../../utils/room';
 import { StateEvent } from '../../../types/matrix/room';
 import {
+  filterGroupsByDateRange,
   filterGroupsByMsgType,
   filterGroupsByPinned,
   MessageSearchParams,
@@ -316,12 +317,21 @@ export function MessageSearch({
     getNextPageParam: (lastPage) => lastPage.nextToken,
   });
 
-  // Shared client-side post-filter (msgtype + pinned) applied to BOTH the
-  // server results and the local/encrypted-cache results, so the filter chips
-  // narrow the whole UI consistently rather than only the server section.
+  // Shared client-side post-filter (date range + msgtype + pinned) applied to
+  // BOTH the server results and the local/encrypted-cache results, so the
+  // filter chips narrow the whole UI consistently rather than only the
+  // server section. The date range must be enforced here because the Matrix
+  // search API has no timestamp filter fields (see useMessageSearch.ts); the
+  // local/encrypted path already filters in-range before this runs, so this
+  // is a no-op there and only actually trims the server section.
   const applyResultFilters = useCallback(
     (allGroups: ResultGroup[]): ResultGroup[] => {
-      const byMsgType = filterGroupsByMsgType(allGroups, msgTypeFilters);
+      const inDateRange = filterGroupsByDateRange(
+        allGroups,
+        msgSearchParams.fromTs,
+        msgSearchParams.toTs,
+      );
+      const byMsgType = filterGroupsByMsgType(inDateRange, msgTypeFilters);
       if (!pinnedOnly) return byMsgType;
       // Build a per-room pinned-event lookup. Heavy Matrix reads stay here
       // (where `mx` is available); the pure helper only consumes the predicate.
@@ -343,7 +353,7 @@ export function MessageSearch({
       };
       return filterGroupsByPinned(byMsgType, pinnedOnly, isPinned);
     },
-    [msgTypeFilters, pinnedOnly, mx],
+    [msgSearchParams.fromTs, msgSearchParams.toTs, msgTypeFilters, pinnedOnly, mx],
   );
 
   const groups = useMemo(() => {