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. A ZIP with a second image or video, or whose
parts come to more than 20 times its size plus 16 MiB, is refused. 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

@@ -21,11 +21,6 @@ declares one.
 
 # Completed Steps
 
-- 2026-09-28: Tested the live-photo writer's fsyncs (issue 130). A test checks
-  that the image's and the video's temp files are fsynced before either is
-  renamed into place, and the directory after both renames, as the `writeAtomic`
-  test does for one file.
-
 - 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

test/download/download.test.ts

@@ -1909,24 +1909,6 @@ describe("downloadFile live photos", () => {
         ]);
     });
 
-    it("fsyncs each part's temp file before the renames and the directory after", async () => {
-        const t = setup(livePhotoZip(), livePhoto);
-
-        await t.run();
-
-        // The same durability contract as `writeAtomic`, for two files: both
-        // temp files are on disk before either is renamed into place, and the
-        // directory is fsynced once both renames are done.
-        const [imageTmp, videoTmp] = renameHook.calls.map((c) => c.from);
-        expect(durabilityHook.events).toEqual([
-            `sync:w:${imageTmp}`,
-            `sync:w:${videoTmp}`,
-            `rename:${join(t.dir, "f.heic")}`,
-            `rename:${join(t.dir, "f.mov")}`,
-            `sync:r:${t.dir}`,
-        ]);
-    });
-
     it("stores neither part when the video cannot be renamed into place", async () => {
         const t = setup(livePhotoZip(), livePhoto);
         renameHook.failWith = new Error("simulated rename failure");

test/thumbnails/thumbnails.test.ts

@@ -787,13 +787,12 @@ describe("fixMissingThumbnails", () => {
     });
 
     it("re-encodes smaller until the thumbnail fits the recorded size", async () => {
-        // A noisy 64x48 JPEG, which the default encoding (quality 50, not
+        // A noisy 400x300 JPEG, which the default encoding (quality 50, not
         // resized because it is under 720 px) cannot compress below the size
-        // recorded here: one byte less than that encoding's ciphertext. It is
-        // small so that each encode is quick even on a busy host.
+        // recorded here: one byte less than that encoding's ciphertext.
         const fixMock = await buildThumbMock();
-        const w = 64;
-        const h = 48;
+        const w = 400;
+        const h = 300;
         const noisy = new Uint8Array(
             jpegJs.encode(
                 {