Feature 3: Read-only Google Calendar panel

- CalendarEvent model with summary, start, end, location
- New scope calendar.readonly in SCOPES
- fetch_upcoming_events() in ApiClient (15 events, next 7 days)
- Focus::Calendar variant, Tab cycle includes Calendar
- Body layout: left column split into Tasks (flex) + Calendar (8)
- render_calendar_panel with day headers and scroll
- refresh_calendar() called on initial sync and Ctrl+R
- Up/Down scroll Calendar panel when focused

src/ui/components.rs

@@ -595,6 +595,77 @@ pub fn render_device_auth_popup(
     frame.render_widget(paragraph, popup_area);
 }
 
+pub fn render_calendar_panel(
+    frame: &mut Frame,
+    area: Rect,
+    events: &[CalendarEvent],
+    focused: bool,
+    scroll: u16,
+) {
+    let block = Block::default()
+        .borders(Borders::ALL)
+        .border_style(Style::default().fg(if focused { FOCUS_COLOR } else { Color::DarkGray }))
+        .title(" Calendar ")
+        .title_alignment(Alignment::Left);
+
+    if events.is_empty() {
+        let paragraph = Paragraph::new(Text::from(Line::from(Span::styled(
+            " No upcoming events ",
+            Style::default().fg(Color::DarkGray),
+        ))))
+        .block(block)
+        .alignment(Alignment::Center);
+        frame.render_widget(paragraph, area);
+        return;
+    }
+
+    let mut lines: Vec<Line> = Vec::new();
+    let mut current_date: Option<chrono::NaiveDate> = None;
+
+    for event in events {
+        if let Some(start) = event.start {
+            let event_date = start.date();
+            if Some(event_date) != current_date {
+                current_date = Some(event_date);
+                let day_header = format!(
+                    " --- {} {} --- ",
+                    event_date.format("%A"),
+                    event_date.format("%d/%m"),
+                );
+                lines.push(Line::from(Span::styled(
+                    day_header,
+                    Style::default().fg(Color::Gray),
+                )));
+            }
+
+            let time_str = start.format("%H:%M").to_string();
+            let summary = &event.summary;
+            let line_text = if summary.len() > 30 {
+                format!(" {} {:.30}…", time_str, summary)
+            } else {
+                format!(" {} {}", time_str, summary)
+            };
+            lines.push(Line::from(Span::styled(
+                line_text,
+                Style::default().fg(DETAIL_COLOR),
+            )));
+        }
+    }
+
+    let inner_h = (area.height as usize).saturating_sub(2);
+    let visible_lines: Vec<Line> = lines
+        .iter()
+        .skip(scroll as usize)
+        .take(inner_h)
+        .cloned()
+        .collect();
+
+    let paragraph = Paragraph::new(Text::from(visible_lines))
+        .block(block)
+        .scroll((0, 0));
+    frame.render_widget(paragraph, area);
+}
+
 /// Simple word wrap: splits text at word boundaries to fit max_width chars per line
 fn textwrap(text: &str, max_width: usize) -> Vec<String> {
     let mut result = Vec::new();