needs_search sent each video to the image decoders to look for faces; the
decode failed and the photo was left alone only for the session
(scan_failed is in memory), so every launch tried each video again,
silently. Photo::is_video now keeps videos out of the search, as it keeps
them out of the grid's thumbnails. The face search was not part of the
issue this PR fixes; it follows the same rule.
Test: cmd::face_recognize::imp::tests::a_video_is_not_searched_for_faces
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>