scaffold: Epic 1 — project scaffold

Add the full Rust + GTK4 + libadwaita project skeleton:
- Cargo.toml with all dependencies (gtk4 0.11, libadwaita 0.9,
  webkit6 0.6, reqwest, serde, tokio, libsecret)
- build.rs that compiles Blueprint .blp files and bundles a GResource
- data/ui/window.blp — AdwApplicationWindow with AdwNavigationSplitView,
  sidebar with refresh button/spinner and primary menu,
  content page with article menu
- data/resources.gresource.xml bundling UI, HTML, and CSS
- data/net.jeena.FeedTheMonkey.gschema.xml with all GSettings keys
- html/content.html and html/content.css (minimal placeholders)
- src/main.rs, src/app.rs — AdwApplication with APP_ID net.jeena.FeedTheMonkey
- src/window.rs — AdwApplicationWindow GObject subclass loading the
  Blueprint template and persisting window size in GSettings
- COPYING (GPL-3.0) restored from master

The app compiles and the binary is ready to open a blank window.

src/window.rs

@@ -0,0 +1,96 @@
+use gtk4::prelude::*;
+
+glib::wrapper! {
+    pub struct FeedTheMonkeyWindow(ObjectSubclass<imp::FeedTheMonkeyWindow>)
+        @extends libadwaita::ApplicationWindow, gtk4::ApplicationWindow, gtk4::Window, gtk4::Widget,
+        @implements gio::ActionGroup, gio::ActionMap, gtk4::Accessible, gtk4::Buildable,
+                    gtk4::ConstraintTarget, gtk4::Native, gtk4::Root, gtk4::ShortcutManager;
+}
+
+impl FeedTheMonkeyWindow {
+    pub fn new(app: &libadwaita::Application) -> Self {
+        glib::Object::builder()
+            .property("application", app)
+            .build()
+    }
+}
+
+mod imp {
+    use super::*;
+    use gtk4::CompositeTemplate;
+    use libadwaita::subclass::prelude::*;
+
+    #[derive(CompositeTemplate, Default)]
+    #[template(resource = "/net/jeena/FeedTheMonkey/ui/window.ui")]
+    pub struct FeedTheMonkeyWindow {
+        #[template_child]
+        pub toast_overlay: TemplateChild<libadwaita::ToastOverlay>,
+        #[template_child]
+        pub split_view: TemplateChild<libadwaita::NavigationSplitView>,
+        #[template_child]
+        pub refresh_stack: TemplateChild<gtk4::Stack>,
+        #[template_child]
+        pub refresh_button: TemplateChild<gtk4::Button>,
+        #[template_child]
+        pub content_page: TemplateChild<libadwaita::NavigationPage>,
+        #[template_child]
+        pub article_menu_button: TemplateChild<gtk4::MenuButton>,
+    }
+
+    #[glib::object_subclass]
+    impl ObjectSubclass for FeedTheMonkeyWindow {
+        const NAME: &'static str = "FeedTheMonkeyWindow";
+        type Type = super::FeedTheMonkeyWindow;
+        type ParentType = libadwaita::ApplicationWindow;
+
+        fn class_init(klass: &mut Self::Class) {
+            klass.bind_template();
+        }
+
+        fn instance_init(obj: &glib::subclass::InitializingObject<Self>) {
+            obj.init_template();
+        }
+    }
+
+    impl ObjectImpl for FeedTheMonkeyWindow {
+        fn constructed(&self) {
+            self.parent_constructed();
+            self.restore_window_state();
+        }
+    }
+
+    impl FeedTheMonkeyWindow {
+        fn restore_window_state(&self) {
+            let settings = gio::Settings::new("net.jeena.FeedTheMonkey");
+            let window = self.obj();
+
+            let width = settings.int("window-width");
+            let height = settings.int("window-height");
+            let maximized = settings.boolean("window-maximized");
+
+            window.set_default_size(width, height);
+            if maximized {
+                window.maximize();
+            }
+
+            // Save state when the window closes
+            let settings_clone = settings.clone();
+            window.connect_close_request(move |win| {
+                if !win.is_maximized() {
+                    let (w, h) = (win.width(), win.height());
+                    settings_clone.set_int("window-width", w).ok();
+                    settings_clone.set_int("window-height", h).ok();
+                }
+                settings_clone
+                    .set_boolean("window-maximized", win.is_maximized())
+                    .ok();
+                glib::Propagation::Proceed
+            });
+        }
+    }
+
+    impl WidgetImpl for FeedTheMonkeyWindow {}
+    impl WindowImpl for FeedTheMonkeyWindow {}
+    impl ApplicationWindowImpl for FeedTheMonkeyWindow {}
+    impl AdwApplicationWindowImpl for FeedTheMonkeyWindow {}
+}