Improve timeline scroll, media layout, avatars, and emoji coverage.

Remember room scroll position across switches, reserve image/video heights from Matrix dimensions, cache authenticated media blobs for avatars, restore jumbo emoji-only messages, and extend emoji font unicode-range for Unicode 15 glyphs.

src/app/utils/common.ts

@@ -87,6 +87,23 @@ export const scaleYDimension = (x: number, scaledX: number, y: number): number =
   return scaleFactor * y;
 };
 
+/** Fit natural media size into a max box without upscaling. */
+export const fitMediaSize = (
+  w: number,
+  h: number,
+  maxW: number,
+  maxH: number
+): { width: number; height: number } => {
+  if (w <= 0 || h <= 0) {
+    return { width: maxW, height: Math.round(maxW * 0.75) };
+  }
+  const scale = Math.min(maxW / w, maxH / h, 1);
+  return {
+    width: Math.max(1, Math.round(w * scale)),
+    height: Math.max(1, Math.round(h * scale)),
+  };
+};
+
 export const parseGeoUri = (location: string) => {
   const [, data] = location.split(':');
   const [cords] = data.split(';');