feat(search): sender picker, date presets, has:link filter

- Add SelectSenderButton: clickable people picker for the From filter
  replacing the text-only from:@user syntax
- Add date preset shortcuts in DateRangeButton (Today, Last week,
  Last month, Last year) for one-click range selection
- Add Has link chip backed by Matrix contains_url API filter; toggle
  removes cleanly with X badge
- Wire containsUrl through URL params, useMessageSearch hook, and
  SearchFilters props

UNTESTED — verify at chat.lotusguild.org post-deploy.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

LOTUS_TODO.md

@@ -188,10 +188,19 @@ Features:
 **What:** Implement a persistent local cache for search results, optimized for encrypted rooms.  
 **Approach:** Use `IndexedDB` to store search metadata (event IDs, timestamps) to prevent redundant server-side decryption/fetching.
 
-### [ ] P4-9 · Advanced Search Filter UI
+### [x] P4-9 · Advanced Search Filter UI — PARTIALLY DONE (UNTESTED)
 
-**What:** Introduce a more robust search filter UI in `SearchFilters.tsx`.  
-**Approach:** Add UI components for easier filtering and a visual date-range picker that correctly maps to `fromTs` and `toTs`.
+**What:** Improve search filter UX in `SearchFilters.tsx`.  
+**Completed 2026-06-18:**
+- ✅ `SelectSenderButton` — picker UI for sender filter (previously required typing `from:@user` by hand)
+- ✅ `DateRangeButton` — quick-pick presets: Today / Last week / Last month / Last year
+- ✅ `Has link` chip — `contains_url: true` filter, wired to Matrix API and URL param
+**UNTESTED** — needs verification at chat.lotusguild.org.
+
+**Remaining for parity with Discord/Slack:**
+- [ ] `has:image` / `has:file` / `has:video` — msgtype filters (require client-side post-filtering, no server API)
+- [ ] Pinned messages filter
+- [ ] Saved searches / search history
 
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