Add FUSE fix wizard with pkexec installation

Dashboard shows a banner when FUSE is not functional. The wizard
detects the distro, shows the install command, and runs it via pkexec.
Verifies FUSE status after installation completes.

src/ui/dashboard.rs

@@ -26,6 +26,18 @@ pub fn build_dashboard_page(db: &Rc<Database>) -> adw::NavigationPage {
         .margin_end(18)
         .build();
 
+    // FUSE warning banner if not functional
+    let fuse_info = fuse::detect_system_fuse();
+    if !fuse_info.status.is_functional() {
+        let banner = adw::Banner::builder()
+            .title("FUSE is not working - some AppImages may not launch")
+            .button_label("Fix Now")
+            .revealed(true)
+            .build();
+        banner.set_action_name(Some("win.fix-fuse"));
+        content.append(&banner);
+    }
+
     // Section 1: System Status
     content.append(&build_system_status_group());