Store live photos as their image and their video (closes #107)

A live photo, which Ente stores as one ZIP, is unpacked as it downloads
into its image and its video, each `<fileID>.<ext>` with its extension
from the ZIP, beside `<fileID>.livephoto.json`, which names the two.
Both are checked against the recorded hash and renamed into place only
when both are complete. The backup and the content cache count a live
photo as stored only with both files, album folders link both,
`quak get` writes both, and the content result gives the video as
`videoPath`. A ZIP an earlier version stored is replaced.

Model: opus-5-5

TODO.md

@@ -14,15 +14,25 @@ pre-1.0
 
 # Next Step
 
-Store live photos in a form a photo viewer can open
-(https://git.eeqj.de/sneak/quak/issues/107). This waits on sneak's choice
-between keeping the ZIP and unpacking it into the image and the video.
+None: every issue still open is done on `next` or `next2` and waits for it to
+reach `main`.
 
 Tagging and releases are decided by sneak alone, and happen only when he
 declares one.
 
 # Completed Steps
 
+- 2026-09-23: Live photos are stored as their image and their video (issue 107).
+  A live photo, which Ente stores as one ZIP, is unpacked as it downloads into
+  `<fileID>.<ext>` for the image and for the video, each with its extension from
+  the ZIP, beside `<fileID>.livephoto.json`, which names the two. Both are
+  checked against the recorded hash and renamed into place only when both are
+  complete. The backup and the content cache count the live photo as stored only
+  with both files, the album folder links both, `quak get` writes both, and the
+  content result gives the video as `videoPath`. A ZIP an earlier version stored
+  is replaced on the next backup run, and in the cache when the photo is next
+  read.
+
 - 2026-09-23: Settled the package metadata (issue 6). quak is not published, so
   `package.json` is marked `"private": true` and the `files` field is gone.
   `engines.node` is `>=22`, the major version `script/bootstrap` and the