feat(gui,fuse): delete photos from the gallery and notice remote deletions

The gallery could show photos and nothing else: a photo deleted on the phone
stayed on the page for minutes, and a photo you wanted gone had to be deleted
on another device. Both are now handled here.

Deleting needs a uid-addressed request, because `Request::Delete` takes a
mountpoint path and the photos volume is not in the FUSE mount. `TrashNodes`
trashes through the SDK and answers per-uid outcomes, so a partial failure is
reportable; the daemon then drops those rows with `Db::photos_delete`, album
membership included, rather than leaving the gallery to wait for the next
timeline refresh. The GUI removes the tiles immediately with an Undo toast and
puts back anything the server refused — the photos are in Proton's trash and
stay recoverable there either way. Selection is Ctrl/Shift+click, the Select
toggle or Delete in the lightbox.

Remote deletions arrive on their own now. The Drive volume and the photos
volume have separate event streams, so the photos volume gets its own poller
and its own cursor. Trash and delete events remove rows; anything else only
marks the timeline stale, because there is no inode space to converge on this
volume. With the timeline TTL down to 60 s and an explicit Refresh that waits
for the server instead of only clearing the freshness stamp, a photo deleted
elsewhere leaves the grid in about ten seconds.

crates/pdfs-gui/src/app/pages/photo_viewer.rs

@@ -504,6 +504,7 @@ pub(crate) fn open_photo_viewer(ui: &Rc<Ui>, initial_uid: String) {
     favorite_btn.add_css_class("viewer-action-btn");
 
     let download_btn = action("document-save-symbolic", "Save a copy…");
+    let delete_btn = action("user-trash-symbolic", "Move to Trash (Delete)");
     let open_ext_btn = action("document-open-symbolic", "Open with another app");
     let close_btn = action("window-close-symbolic", "Close (Esc)");
     close_btn.add_css_class("viewer-close-btn");
@@ -516,6 +517,7 @@ pub(crate) fn open_photo_viewer(ui: &Rc<Ui>, initial_uid: String) {
     top_bar.append(&favorite_btn);
     top_bar.append(&info_toggle);
     top_bar.append(&download_btn);
+    top_bar.append(&delete_btn);
     top_bar.append(&open_ext_btn);
     top_bar.append(&close_btn);
     overlay.add_overlay(&top_bar);
@@ -695,6 +697,18 @@ pub(crate) fn open_photo_viewer(ui: &Rc<Ui>, initial_uid: String) {
         });
     });
 
+    // Deleting the photo on screen closes the lightbox: what it was showing is
+    // gone, and leaving it open on a trashed photo invites a second Delete on
+    // something the user cannot see.
+    let ui_delete = ui.clone();
+    let viewer_delete = viewer.clone();
+    let w_delete = window.clone();
+    delete_btn.connect_clicked(move |_| {
+        let uid = viewer_delete.uid.borrow().clone();
+        w_delete.close();
+        trash_photos(&ui_delete, vec![uid]);
+    });
+
     let w_download = window.clone();
     let viewer_download = viewer.clone();
     download_btn.connect_clicked(move |_| {
@@ -757,6 +771,11 @@ pub(crate) fn open_photo_viewer(ui: &Rc<Ui>, initial_uid: String) {
                     w_key.fullscreen();
                 }
             }
+            Some("Delete" | "KP_Delete") => {
+                let uid = viewer_key.uid.borrow().clone();
+                w_key.close();
+                trash_photos(&ui_key, vec![uid]);
+            }
             Some("Escape" | "q") => w_key.close(),
             Some("w") if ctrl => w_key.close(),
             _ => return glib::Propagation::Proceed,