Add note list filtering by sidebar selection

- All Notes → show everything
- People/Events filters → show entities of that type
- Section group header → show all entities of that type
- Specific entity → pinned at top with green border + children
- Topic → show entries whose relatedTo references that topic
- Wikilink reference matching (belongsTo/relatedTo → path stem)

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

src/components/NoteList.css

@@ -72,3 +72,9 @@
 .note-list__status {
   color: #6a6;
 }
+
+.note-list__item--pinned {
+  background: #1e1e3a;
+  border-left: 3px solid #6a6;
+  padding-left: 13px;
+}