Add version rollback support for AppImage updates

src/ui/detail_view.rs

@@ -989,6 +989,56 @@ fn build_system_tab(record: &AppImageRecord, db: &Rc<Database>, toast_overlay: &
     }
     inner.append(&integration_group);
 
+    // Version Rollback group
+    if let Some(ref prev_path) = record.previous_version_path {
+        let prev = std::path::Path::new(prev_path);
+        if prev.exists() {
+            let rollback_group = adw::PreferencesGroup::builder()
+                .title("Version Rollback")
+                .description("A previous version is available from the last update.")
+                .build();
+            let rollback_row = adw::ActionRow::builder()
+                .title("Previous version available")
+                .subtitle(prev_path.as_str())
+                .build();
+            let rollback_btn = gtk::Button::builder()
+                .label("Rollback")
+                .valign(gtk::Align::Center)
+                .css_classes(["destructive-action"])
+                .build();
+            rollback_row.add_suffix(&rollback_btn);
+
+            let current_path = record.path.clone();
+            let prev_path_owned = prev_path.clone();
+            let record_id_rb = record.id;
+            let db_rb = db.clone();
+            let toast_rb = toast_overlay.clone();
+            rollback_btn.connect_clicked(move |btn| {
+                let current = std::path::Path::new(&current_path);
+                let prev = std::path::Path::new(&prev_path_owned);
+                let temp_path = current.with_extension("AppImage.rollback-tmp");
+                // Swap: current -> tmp, prev -> current, tmp -> prev
+                let result = std::fs::rename(current, &temp_path)
+                    .and_then(|_| std::fs::rename(prev, current))
+                    .and_then(|_| std::fs::rename(&temp_path, prev));
+                match result {
+                    Ok(()) => {
+                        db_rb.set_previous_version(record_id_rb, Some(&prev_path_owned)).ok();
+                        toast_rb.add_toast(adw::Toast::new("Rolled back to previous version"));
+                        btn.set_sensitive(false);
+                    }
+                    Err(e) => {
+                        log::error!("Rollback failed: {}", e);
+                        toast_rb.add_toast(adw::Toast::new("Rollback failed"));
+                    }
+                }
+            });
+
+            rollback_group.add(&rollback_row);
+            inner.append(&rollback_group);
+        }
+    }
+
     // Runtime Compatibility group
     let compat_group = adw::PreferencesGroup::builder()
         .title("Compatibility")

src/ui/update_dialog.rs

@@ -184,6 +184,14 @@ fn start_update(
                 dialog.set_body(&success_body);
                 dialog.set_response_enabled("update", false);
 
+                // Save previous version path for rollback
+                if let Some(ref old_path) = applied.old_path_backup {
+                    db_ref.set_previous_version(
+                        record_id,
+                        Some(&old_path.to_string_lossy()),
+                    ).ok();
+                }
+
                 // Handle old version cleanup
                 if let Some(old_path) = applied.old_path_backup {
                     handle_old_version_cleanup(&dialog, old_path);