feat: bookmarks, message scheduling, image compression, room insights

P3-1: Message Bookmarks — right-click any message to bookmark; saved to
io.lotus.bookmarks account data (max 500, syncs across devices); star
icon in sidebar opens BookmarksPanel with filter, Jump-to-message, and
remove buttons; reactive to AccountData events

P3-2: Message Scheduling (MSC4140) — clock button next to send opens
ScheduleMessageModal with datetime-local picker; validates ≥1 min future;
calls PUT org.matrix.msc4140 delayed event API; collapsible
ScheduledMessagesTray above composer lists pending messages with cancel;
local Jotai atom tracks scheduled messages per room

P3-3: File Upload Compression — opt-in checkbox per JPEG/PNG file ≥200KB
in upload preview; canvas API compresses at 0.82 quality; shows before/
after size estimate; compressed blob used in upload when checked

P3-7: Room Insights — new Insights tab in room settings; top 5 active
members (bar chart), top 5 reactions (chips), media breakdown (4 tiles),
24-hour activity heatmap (CSS bar chart); all from local cache only with
disclaimer banner; never the first tab shown

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

src/app/hooks/useBookmarks.ts

@@ -0,0 +1,83 @@
+import { useCallback, useEffect, useState } from 'react';
+import { MatrixClient } from 'matrix-js-sdk';
+import { useMatrixClient } from './useMatrixClient';
+import { useAccountDataCallback } from './useAccountDataCallback';
+
+export type Bookmark = {
+  roomId: string;
+  eventId: string;
+  savedAt: number;
+  previewText: string;
+  roomName: string;
+};
+
+const BOOKMARKS_KEY = 'io.lotus.bookmarks';
+const MAX_BOOKMARKS = 500;
+
+type BookmarksContent = {
+  bookmarks: Bookmark[];
+};
+
+function readBookmarks(mx: MatrixClient): Bookmark[] {
+  return (
+    (mx.getAccountData(BOOKMARKS_KEY as any)?.getContent() as BookmarksContent | undefined)
+      ?.bookmarks ?? []
+  );
+}
+
+export function useBookmarks(): {
+  bookmarks: Bookmark[];
+  addBookmark: (b: Bookmark) => Promise<void>;
+  removeBookmark: (eventId: string) => Promise<void>;
+  isBookmarked: (eventId: string) => boolean;
+} {
+  const mx = useMatrixClient();
+  const [bookmarks, setBookmarks] = useState<Bookmark[]>(() => readBookmarks(mx));
+
+  useAccountDataCallback(
+    mx,
+    useCallback(
+      (evt) => {
+        if (evt.getType() === BOOKMARKS_KEY) {
+          setBookmarks(evt.getContent<BookmarksContent>()?.bookmarks ?? []);
+        }
+      },
+      [setBookmarks],
+    ),
+  );
+
+  // Re-read on mx change
+  useEffect(() => {
+    setBookmarks(readBookmarks(mx));
+  }, [mx]);
+
+  const addBookmark = useCallback(
+    async (b: Bookmark) => {
+      const current = readBookmarks(mx);
+      // Avoid duplicates
+      const filtered = current.filter((bk) => bk.eventId !== b.eventId);
+      let next = [b, ...filtered];
+      if (next.length > MAX_BOOKMARKS) {
+        next = next.slice(0, MAX_BOOKMARKS);
+      }
+      await (mx as any).setAccountData(BOOKMARKS_KEY, { bookmarks: next });
+    },
+    [mx],
+  );
+
+  const removeBookmark = useCallback(
+    async (eventId: string) => {
+      const current = readBookmarks(mx);
+      const next = current.filter((bk) => bk.eventId !== eventId);
+      await (mx as any).setAccountData(BOOKMARKS_KEY, { bookmarks: next });
+    },
+    [mx],
+  );
+
+  const isBookmarked = useCallback(
+    (eventId: string) => bookmarks.some((bk) => bk.eventId === eventId),
+    [bookmarks],
+  );
+
+  return { bookmarks, addBookmark, removeBookmark, isBookmarked };
+}