refactor(gui): extract AppContext for shared page handles

KeysPage::new now takes a single AppContext that owns parent_window,
toast_overlay, and the shared daemon Rc<RefCell<Option<Daemon>>>. Phases
9, 10, 11, and 12 GUI tab will all consume this struct.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

gui/src/app_context.rs

@@ -0,0 +1,27 @@
+//! Shared per-window handles passed to every page constructor.
+//!
+//! `daemon` is a `RefCell<Option<...>>` because the connect-on-startup attempt
+//! may fail (pages render their disconnected banner); a successful Retry
+//! repopulates this same cell, and every page sees the new value via the Rc
+//! clone chain.
+
+use crate::bus::Daemon;
+use std::cell::RefCell;
+use std::rc::Rc;
+
+#[derive(Clone)]
+pub(crate) struct AppContext {
+    pub parent_window: gtk::Window,
+    pub toast_overlay: adw::ToastOverlay,
+    pub daemon: Rc<RefCell<Option<Daemon>>>,
+}
+
+impl AppContext {
+    pub fn new(parent_window: gtk::Window, toast_overlay: adw::ToastOverlay) -> Self {
+        Self {
+            parent_window,
+            toast_overlay,
+            daemon: Rc::new(RefCell::new(None)),
+        }
+    }
+}