feat: add @libre.graph.livePhoto facet to driveItem

[dschmidt]

Description

What are Live Photos?

Apple Live Photos are a pair of files: a still image (HEIC or JPEG) and a
short QuickTime video, captured together and linked by a shared content
identifier (a UUID). On the image it is stored in the Apple maker note,
on the video as com.apple.quicktime.content.identifier. Unlike Google
Motion Photos (#36) there is no single embedded file, the two halves are
separate driveItems.

There is no public file format specification; the metadata keys are
documented as AVFoundation metadata identifiers:
https://developer.apple.com/documentation/avfoundation/avmetadataidentifier

What this PR adds

A new read-only @libre.graph.livePhoto facet on driveItem, following the
@libre.graph.motionPhoto pattern. Facet presence means the item was
captured as part of a Live Photo; the counterpart is the driveItem whose
facet carries the same contentId.

Property	Type	Description
contentId	string (required)	UUID shared by both halves, used for pairing. Required: facet presence means the identifier was found.
stillImageTimeUs	integer (int64)	Time in microseconds within the video at which the still was captured. Comes from the video file only; absent until the extraction side supports it (see below).
auto	boolean	Auto Live Photo mode flag (video half only).
vitalityScore	number (double)	0..1 score of how interesting the clip is, used for autoplay decisions (video half only).
vitalityScoringVersion	integer (int64)	Version of the scoring algorithm (video half only).

Example response

{
  "@libre.graph.livePhoto": {
    "contentId": "CD28D161-D5EC-4CDE-8B60-DACCC1363B6B",
    "stillImageTimeUs": 1233333,
    "auto": true,
    "vitalityScore": 0.9398496,
    "vitalityScoringVersion": 4
  }
}

Validated with openapi-generator-cli v7.13.0 (validate plus a go client
generation smoke test; the generated model and driveItem wiring look as
expected).

Metadata extraction prerequisites on the server side: the video-side keys
are covered by apache/tika#2935, the image-side
Live Photo video index additionally needs
drewnoakes/metadata-extractor#739 (tracked in
https://issues.apache.org/jira/browse/TIKA-4776). stillImageTimeUs is
specified now but will stay absent until the extraction side can parse
the com.apple.quicktime.still-image-time timed metadata track (mebx)
of the video. The image side offers no reliable source: the Apple maker
note tag 0x0017, historically documented as a derivable video index,
does not encode a usable time on current iOS versions.

[Copilot]

Pull request overview

Adds a new read-only @libre.graph.livePhoto facet to the driveItem schema to expose Apple Live Photo pairing metadata (via a shared contentId), mirroring the existing @libre.graph.motionPhoto extension approach.

Changes:

• Add @libre.graph.livePhoto facet to driveItem referencing a new livePhoto schema.
• Introduce components.schemas.livePhoto with contentId plus optional video-half metadata fields (stillImageTimeUs, auto, vitalityScore, vitalityScoringVersion).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.