UI: update notice, Help › Check for Updates and Reinstall, Settings › Updates (#231)

The window checks at start-up at most once a day when automatic checks are on (Settings and
the first run's question), never while that question is open and never without a host, so the
browser and tests make no network call. A newer release shows a quiet notice in the status bar
("FieldCraft X is available — What's new · Install · Skip"); Install downloads and verifies
through the host, then asks to restart, saving or asking about unsaved changes first, and the
host swaps the release in after the window closes. A .deb/.rpm install offers the system's
installer and the command instead. Skip this version is kept in the preferences.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/ui-egui/src/palette.rs

@@ -156,6 +156,7 @@ pub fn command_line(app: &mut ModelApp, ui: &mut egui::Ui) {
                     ui.separator();
                     ui.label(RichText::new(format!("{nodes} nodes  {elements} elements")).size(11.5).color(t.text_dim));
                     ui.separator();
+                    crate::updates::notice(app, ui);
                     let (text, color) = match &app.status {
                         Some(s) => (s.text.as_str(), if s.error { t.error } else { t.text }),
                         None => ("Ready", t.text_dim),