feat(core,fuse,gui,cli): filter the photos timeline to photos in no album

A new pill next to the favorites filter narrows the timeline to the photos
no album of ours holds yet, so what is left to file is easy to find. A
RAW+JPEG pair counts as filed when any of its files is in an album.

PhotosTimeline gains an optional not_in_album flag; older front-ends omit it
and get the whole timeline. Album contents are fetched lazily, so the first
filtered page fetches the contents of any album not yet listed. Photos added
to an album while the filter is on leave the timeline at once.

crates/pdfs-core/src/control.rs

@@ -67,6 +67,10 @@ pub enum Request {
         /// get the whole timeline, as before.
         #[serde(default)]
         favorites: bool,
+        /// Restrict the page to photos no album of ours holds — what is left to
+        /// file. Older front-ends omit it and get the whole timeline, as before.
+        #[serde(default)]
+        not_in_album: bool,
     },
     /// Every photo of one photo's group — the JPEG and the RAW of one shot, a
     /// live photo and its clip. Replies with [`Response::Photos`], holding one
@@ -2790,6 +2794,7 @@ mod tests {
             decoded,
             Request::PhotosTimeline {
                 favorites: false,
+                not_in_album: false,
                 kind: None,
                 range: None,
                 ..