* android, desktop: fix video preview expanding into empty black area
The video message box (CHAT_IMAGE_LAYOUT_ID) never gave itself a definite
height - it took the height of its tallest child. That child is the player
surface, which has no stable intrinsic height until playback starts: on
Android an unprepared StyledPlayerView reports no video size, so its
AspectRatioFrameLayout (RESIZE_MODE_FIXED_WIDTH, aspect 0) does not shrink.
Before #6726 this was masked: the box was measured with unbounded height, so
the surface collapsed to 0. #6726 bounded the box to 2.33x width to constrain
tall images, and the unprepared surface then expanded to fill that height,
showing as a long empty black strip below the preview once a video downloads.
Give the box a definite size from the preview aspect ratio, mirroring
CIImageView. Height follows the measured (clamped) width via Modifier.layout
so wide videos on narrow screens don't leave an empty strip (the #7223 fix).
* plans: justify video preview black-area fix
