feat(ui): include app version in header title

Add `APP_VERSION` constant derived from `CARGO_PKG_VERSION` and update the header rendering to display the version (e.g., “🦉 OWLEN v1.2.3 – AI Assistant”).

crates/owlen-tui/src/ui.rs

@@ -24,6 +24,7 @@ use owlen_core::ui::{FocusedPanel, InputMode, RoleLabelDisplay};
 use textwrap::wrap;
 
 const PRIVACY_TAB_INDEX: usize = HELP_TAB_COUNT - 1;
+const APP_VERSION: &str = env!("CARGO_PKG_VERSION");
 
 fn focus_beacon_span(is_active: bool, is_focused: bool, theme: &Theme) -> Span<'static> {
     if !is_active {
@@ -1111,7 +1112,7 @@ fn wrap_line_segments(line: &str, width: usize) -> Vec<String> {
 fn render_header(frame: &mut Frame<'_>, area: Rect, app: &ChatApp) {
     let theme = app.theme();
     let title_span = Span::styled(
-        " 🦉 OWLEN - AI Assistant ",
+        format!(" 🦉 OWLEN v{} – AI Assistant ", APP_VERSION),
         Style::default()
             .fg(theme.focused_panel_border)
             .add_modifier(Modifier::BOLD),