fix(core,fuse,gui): date photos by their EXIF when nothing else does

A Takeout photo with no sidecar and no date in its name was filed under
the day of the import, and the app dated uploads by modification time.
A new `exiftime` module reads DateTimeOriginal (then DateTimeDigitized)
with its offset. Takeout uses it for undated photos it copies out for a
thumbnail, and the daemon uses it for app uploads before falling back to
the modification time (B244).

Cargo.lock

@@ -3497,6 +3497,7 @@ dependencies = [
  "dbus-secret-service-keyring-store",
  "directories",
  "ignore",
+ "kamadak-exif",
  "keyring-core",
  "libc",
  "parking_lot",