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/utils/imageCompression.ts

@@ -0,0 +1,69 @@
+export type CompressionResult = {
+  blob: Blob;
+  originalSize: number;
+  compressedSize: number;
+  width: number;
+  height: number;
+};
+
+const COMPRESSIBLE_TYPES = ['image/jpeg', 'image/png'];
+const COMPRESSION_SKIP_THRESHOLD = 200 * 1024; // 200 KB
+
+/** Returns true if this file type can be compressed AND the file is large enough to bother. */
+export function isCompressible(file: File): boolean {
+  return COMPRESSIBLE_TYPES.includes(file.type) && file.size >= COMPRESSION_SKIP_THRESHOLD;
+}
+
+/**
+ * Compress an image file via canvas.toBlob.
+ * Returns null if the file type is not compressible (GIF, SVG, WebP, video, audio, etc.).
+ */
+export async function compressImage(file: File, quality = 0.82): Promise<CompressionResult | null> {
+  if (!COMPRESSIBLE_TYPES.includes(file.type)) return null;
+
+  const img = await loadImage(file);
+  const canvas = document.createElement('canvas');
+  canvas.width = img.naturalWidth;
+  canvas.height = img.naturalHeight;
+  const ctx = canvas.getContext('2d')!;
+  ctx.drawImage(img, 0, 0);
+
+  return new Promise((resolve) => {
+    canvas.toBlob(
+      (blob) => {
+        if (!blob) {
+          resolve(null);
+          return;
+        }
+        resolve({
+          blob,
+          originalSize: file.size,
+          compressedSize: blob.size,
+          width: img.naturalWidth,
+          height: img.naturalHeight,
+        });
+      },
+      'image/jpeg',
+      quality,
+    );
+  });
+}
+
+function loadImage(file: File): Promise<HTMLImageElement> {
+  return new Promise((resolve, reject) => {
+    const url = URL.createObjectURL(file);
+    const img = new Image();
+    img.onload = () => {
+      URL.revokeObjectURL(url);
+      resolve(img);
+    };
+    img.onerror = reject;
+    img.src = url;
+  });
+}
+
+export function formatFileSize(bytes: number): string {
+  if (bytes < 1024) return `${bytes} B`;
+  if (bytes < 1024 * 1024) return `${(bytes / 1024).toFixed(1)} KB`;
+  return `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
+}