Fix embedding/playback of portrait 4K videos, bump max video resolution to 8K

[comdev1337]

Fixes #30678
See: #30678 (comment)

• FFmpeg may validate decoder-allocation dimensions, not just visible frame dimensions. Some H.264/HEVC frames are internally padded for alignment, so a visible 2160x3840 frame can trip max_pixels even though 2160 * 3840 == 3840 * 2160. The patch keeps Telegram’s real visible-frame validation intact, but gives FFmpeg max_pixels a small alignment slack.
• The upload/playback frame-area cap is raised from 4K to 8K, 7680x4320 videos can be embedded
• 8K videos must not allocate full-size ARGB thumbnails/cover frames during inspection. A full 7680x4320 BGRA image is ~126 MiB and exceeds the existing 64 MiB frame-storage check, so the patch renders small thumbnail/cover frames while preserving the real video dimensions separately.
• Video document attributes now use the decoded video dimensions, not the generated thumbnail size, so scaled-down thumbnails do not accidentally turn an 8K video into 320x180 metadata.
• Playback startup now reads dimensions from the decoded frame metadata first and waits for the UI’s requested render size before allocating image storage, avoiding full-resolution first-frame allocation.

[john-preston]

Thanks for fixing the regression. But other changes I don't think are desired right now, they can be discussed, but separate from regression fix for the files that played before but stopped playing in the latest version.

I don't want to raise sending / playable files dimensions to 8K, they were never sent / played before and this change has nothing to do with recent regression. Also, rendering the initial frame in streaming downscaled to isn't what I want, because I cache that frame separately as a "full first frame", and 320x320 won't be good for most of the videos.

[john-preston]

For now I've merged the fixing regression part.

[comdev1337]

Fair enough, I should have split these. Removed the 665a288 part.

Also, rendering the initial frame in streaming downscaled to isn't what I want, because I cache that frame separately as a "full first frame", and 320x320 won't be good for most of the videos.

Bumped kMaxFrameStorageBytes to 128 MiB instead

[kalandrack69]

Day