fix: audit fixes — RefCell across await, async avatar decode (v0.6.10)

- init_fingerprint_async: hoist username before the await so a concurrent
  connect_monitor signal (hotplug / suspend-resume) cannot cause a RefCell
  panic. Re-borrow after the await for signal wiring.
- set_avatar_from_file: decode via gio::File::read_future +
  Pixbuf::from_stream_at_scale_future so the GTK main thread stays
  responsive during monitor hotplug. Default icon shown while loading.

src/main.rs

@@ -168,32 +168,38 @@ fn init_fingerprint_async(
         let mut listener = FingerprintListener::new();
         listener.init_async().await;
 
-        let handles = all_handles.borrow();
-        if handles.is_empty() {
-            return;
-        }
+        // Extract username without holding a borrow across the await below —
+        // otherwise a concurrent connect_monitor signal (hotplug / suspend-resume)
+        // that tries to borrow_mut() panics at runtime.
+        let username = {
+            let handles = all_handles.borrow();
+            if handles.is_empty() {
+                return;
+            }
+            let u = handles[0].username.clone();
+            if u.is_empty() {
+                return;
+            }
+            u
+        };
 
-        // Use the first monitor's username to check enrollment
-        let username = &handles[0].username;
-        if username.is_empty() {
-            return;
-        }
-
-        if !listener.is_available_async(username).await {
+        if !listener.is_available_async(&username).await {
             log::debug!("fprintd not available or no enrolled fingers");
             return;
         }
 
         let fp_rc = Rc::new(RefCell::new(listener));
 
-        // Show fingerprint label on all existing monitors
-        for h in handles.iter() {
-            lockscreen::show_fingerprint_label(h, &fp_rc);
+        // Re-borrow after the await — no further awaits in this scope, so it is
+        // safe to hold the borrow briefly while wiring up the labels.
+        {
+            let handles = all_handles.borrow();
+            for h in handles.iter() {
+                lockscreen::show_fingerprint_label(h, &fp_rc);
+            }
+            lockscreen::start_fingerprint(&handles[0], &fp_rc);
         }
 
-        // Start verification listener on the first monitor only
-        lockscreen::start_fingerprint(&handles[0], &fp_rc);
-
         // Publish the listener so hotplugged monitors get FP labels too
         *shared_fp.borrow_mut() = Some(fp_rc);
     });