fix(core,fuse,gui): UI/UX quick wins from the audit (phase 0)

- Move Google Takeout import out of Settings; Photos owns it, and the
  Takeout page's back button returns there.
- Trash from the file browser is Undo-only (no confirm); F2 on a
  multi-selection explains why it does nothing.
- Ask before sign-out, rejecting an invitation, removing someone's access,
  removing a public link, and switching a folder to on-demand.
- Clearer offline wording ("Make available offline" / "Make online only")
  with dedicated offline, online-only and upload symbolic icons; the pin row
  is hidden for folders.
- Search hits report whether a file is cached, so search results show the
  offline badge.
- Activity log: readable Empty Trash / link entries, distinct icons, and
  error/warning styling for failures and conflicts.
- Proper singular/plural counts instead of "item(s)" / "archive(s)".
- Name earlier versions by save time instead of revision id; capitalise
  the public link role; stop-syncing uses a stop icon, not a trash can.
- Label the Photos Upload and "Show on map" buttons; toast when a
  thumbnail build finishes; the versions button follows the mount state.
- Mode switches and device mutations reload both sync pages.

crates/pdfs-fuse/src/control.rs

@@ -810,9 +810,14 @@ fn handle_control_conn(core: &Core, username: &str, mountpoint: &Path, stream: U
         },
         Ok(CtlRequest::EmptyTrash) => match core.empty_trash() {
             Ok(n) => {
-                core.log_activity(ActivityKind::EmptyTrash, format!("{n} item(s)"), "", true);
+                let items = if n == 1 {
+                    "1 item".to_string()
+                } else {
+                    format!("{n} items")
+                };
+                core.log_activity(ActivityKind::EmptyTrash, items.clone(), "", true);
                 CtlResponse::Ok {
-                    message: format!("emptied trash ({n} item(s))"),
+                    message: format!("emptied trash ({items})"),
                 }
             }
             Err(e) => CtlResponse::error(e),

crates/pdfs-fuse/src/lib.rs

@@ -3865,6 +3865,12 @@ impl Core {
                 size: node_size(&h.node),
                 modified: h.node.modification_time,
                 pinned: pinned.contains(&h.node.uid.to_string()),
+                cached: !h.node.is_folder()
+                    && self.cache.is_cached(
+                        &h.node.uid,
+                        h.node.modification_time,
+                        node_size(&h.node),
+                    ),
                 uid: h.node.uid.to_string(),
                 mounted_path: roots.resolve(&h.path),
                 path: h.path,
@@ -3932,6 +3938,12 @@ impl Core {
                         size: node_size(&hit.node),
                         modified: hit.node.modification_time,
                         pinned: is_pinned,
+                        cached: !hit.node.is_folder()
+                            && self.cache.is_cached(
+                                &hit.node.uid,
+                                hit.node.modification_time,
+                                node_size(&hit.node),
+                            ),
                         uid,
                         mounted_path: roots.resolve(&hit.path),
                         path: hit.path,