Embed face regions in videos instead of API re-linking (issue #30)

[Majorfi]

Follow-up to #30. Addresses @Nurgak's report that video faces are "still not embedded in videos" on v1.0.4.

Why

v1.0.4 preserved video people by re-creating them over POST /faces after re-upload (recreateFaces). That is Immich-internal only — it never writes anything to the file. So Nurgak's observation is literally correct: nothing lands in the video file, and there's no portable, transfer-surviving metadata (unlike the image path).

It turns out that assumption — "MWG regions are image-only" — was wrong. Immich's metadata face importer reads RegionInfo from a video container just as it does from an image (getExifTags runs readTags on all asset types; applyTaggedFaces has no image gate). Verified end-to-end against a live Immich v3.0.1 server: a re-uploaded .mp4 with an embedded region comes back with a sourceType: exif face linked to the person.

What

Videos now embed the same MWG regions as images and re-import them when "Import faces from metadata" is on — the same round trip photos already rely on, and portable (survives sharing, readable by digiKam).

• HasFaceRegionsToEmbed accepts mp4/mov/m4v; other containers are skipped.
• A video has no EXIF Orientation, so regionOrientation reads the QuickTime Rotation tag and maps it to the equivalent orientation (videoRotationToOrientation: 0°→1, 90°→6, 270°→8), feeding the existing rasterRegion inverse — no new coordinate math.
• 180° / non-cardinal rotation is left un-embedded. Live testing showed Immich re-orients 90°/270° video regions on import but not 180°, so writing a 180° region would misplace the box. Landscape and both portrait orientations are covered.
• Removes the API re-link path entirely (recreateFaces, CreateFace, the finalizeReplacement hook, the Faces uploader field). Embedding + re-link together would double-create faces (one exif, one manual) when the import setting is on; embedding alone is consistent with how images already behave.

Net −369 lines.

Validation

End-to-end on a live Immich v3.0.1: ran -faces on a real video → the file gained Facu, Gui, Karlen regions → the re-uploaded asset shows 3 sourceType: exif faces for those people. Rotation mapping (0/90/270 import correctly; 180 anomalous) confirmed by uploading tagged videos and reading back the imported boxes. go vet, gofmt, full suite green; new unit tests cover the rotation mapping and the video embeddability gate.

Note

This relies on the server's "Import faces from metadata" setting, exactly as the image path already does. A server with it off keeps the regions in the file (portable / other tools) but won't surface them in Immich — same behavior as photos.