Wire backup, notification, report export, and file watcher modules into UI

- Add export button to security report page (HTML/JSON/CSV via FileDialog)
- Send desktop notifications after security scans when enabled in settings
- Add backup section to storage tab with create/restore/delete and toast feedback
- Start file watcher on launch to auto-refresh library on AppImage changes
- Fix detail view tabs requesting tallest tab height (set vhomogeneous=false)
- Disable tab transitions to avoid visual glitch with variable-height tabs

src/window.rs

@@ -11,9 +11,11 @@ use crate::core::database::Database;
 use crate::core::discovery;
 use crate::core::integrator;
 use crate::core::launcher;
+use crate::core::notification;
 use crate::core::orphan;
 use crate::core::security;
 use crate::core::updater;
+use crate::core::watcher;
 use crate::i18n::{i18n, ni18n_f};
 use crate::ui::cleanup_wizard;
 use crate::ui::dashboard;
@@ -37,6 +39,7 @@ mod imp {
         pub database: OnceCell<Rc<Database>>,
         pub drop_overlay: OnceCell<gtk::Box>,
         pub drop_revealer: OnceCell<gtk::Revealer>,
+        pub watcher_handle: std::cell::RefCell<Option<notify::RecommendedWatcher>>,
     }
 
     impl Default for DriftwoodWindow {
@@ -49,6 +52,7 @@ mod imp {
                 database: OnceCell::new(),
                 drop_overlay: OnceCell::new(),
                 drop_revealer: OnceCell::new(),
+                watcher_handle: std::cell::RefCell::new(None),
             }
         }
     }
@@ -705,6 +709,19 @@ impl DriftwoodWindow {
                                 let msg = format!("Found {} CVE{}", total, if total == 1 { "" } else { "s" });
                                 toast_overlay.add_toast(adw::Toast::new(&msg));
                             }
+
+                            // Send desktop notifications for new CVE findings if enabled
+                            let settings = gio::Settings::new(APP_ID);
+                            if settings.boolean("security-notifications") {
+                                let threshold = settings.string("security-notification-threshold").to_string();
+                                glib::spawn_future_local(async move {
+                                    let _ = gio::spawn_blocking(move || {
+                                        let bg_db = Database::open().expect("Failed to open database");
+                                        notification::check_and_notify(&bg_db, &threshold);
+                                    })
+                                    .await;
+                                });
+                            }
                         }
                         _ => toast_overlay.add_toast(adw::Toast::new("Security scan failed")),
                     }
@@ -816,6 +833,9 @@ impl DriftwoodWindow {
         // Always scan on startup to discover new AppImages and complete pending analyses
         self.trigger_scan();
 
+        // Start watching scan directories for new AppImage files
+        self.start_file_watcher();
+
         // Check for orphaned desktop entries in the background
         let toast_overlay = self.imp().toast_overlay.get().unwrap().clone();
         glib::spawn_future_local(async move {
@@ -1019,6 +1039,44 @@ impl DriftwoodWindow {
         });
     }
 
+    fn start_file_watcher(&self) {
+        let settings = self.settings();
+        let dirs: Vec<std::path::PathBuf> = settings
+            .strv("scan-directories")
+            .iter()
+            .map(|s| discovery::expand_tilde(&s.to_string()))
+            .collect();
+
+        if dirs.is_empty() {
+            return;
+        }
+
+        // Use an atomic flag to communicate across the thread boundary.
+        // The watcher callback (on a background thread) sets the flag,
+        // and a glib timer on the main thread polls and dispatches.
+        let changed = std::sync::Arc::new(std::sync::atomic::AtomicBool::new(false));
+
+        let changed_watcher = changed.clone();
+        let handle = watcher::start_watcher(dirs, move |_event| {
+            changed_watcher.store(true, std::sync::atomic::Ordering::Relaxed);
+        });
+
+        if let Some(h) = handle {
+            self.imp().watcher_handle.replace(Some(h));
+
+            // Poll the flag every second from the main thread
+            let window_weak = self.downgrade();
+            glib::timeout_add_local(std::time::Duration::from_secs(1), move || {
+                if changed.swap(false, std::sync::atomic::Ordering::Relaxed) {
+                    if let Some(window) = window_weak.upgrade() {
+                        window.trigger_scan();
+                    }
+                }
+                glib::ControlFlow::Continue
+            });
+        }
+    }
+
     fn show_shortcuts_dialog(&self) {
         let dialog = adw::Dialog::builder()
             .title("Keyboard Shortcuts")