Feature 3: relative due dates right-aligned in task list

- Replace absolute date with relative string (Overdue, Xh left, X days left)
- Overdue in Red, <24h in Yellow, >=24h in DarkGray
- Due string right-aligned via padding calculation

src/ui/components.rs

@@ -49,6 +49,24 @@ pub fn render_tabs_bar(
     frame.render_widget(tabs, area);
 }
 
+fn relative_due_str(due: chrono::NaiveDateTime) -> (String, Color) {
+    let now = chrono::Local::now().naive_local();
+    let diff = due - now;
+
+    if diff < chrono::Duration::zero() {
+        (" Overdue ".to_string(), Color::Red)
+    } else if diff < chrono::Duration::hours(24) {
+        let hours = diff.num_hours();
+        (format!(" {}h left ", hours), Color::Yellow)
+    } else {
+        let days = diff.num_days();
+        (
+            format!(" {} day{} left ", days, if days == 1 { "" } else { "s" }),
+            Color::DarkGray,
+        )
+    }
+}
+
 pub fn render_task_list(
     frame: &mut Frame,
     area: Rect,
@@ -61,6 +79,8 @@ pub fn render_task_list(
     let done = tasks.iter().filter(|t| t.status == TaskStatus::Completed).count();
     let todo = total - done;
 
+    let content_width = (area.width as usize).saturating_sub(5);
+
     let items: Vec<ListItem> = tasks
         .iter()
         .map(|task| {
@@ -69,12 +89,12 @@ pub fn render_task_list(
                 TaskStatus::NeedsAction => "[ ]",
             };
 
-            let due_str = task
+            let (due_text, due_color) = task
                 .due
-                .map(|d| d.format(" %d/%m/%Y %H:%M").to_string())
-                .unwrap_or_default();
+                .map(relative_due_str)
+                .unwrap_or((String::new(), Color::DarkGray));
 
-            let content = Line::from(vec![
+            let mut spans = vec![
                 Span::styled(
                     format!("{} ", checkbox),
                     Style::default().fg(if task.status == TaskStatus::Completed {
@@ -93,12 +113,16 @@ pub fn render_task_list(
                         },
                     ),
                 ),
-                Span::styled(
-                    due_str,
-                    Style::default().fg(Color::DarkGray),
-                ),
-            ]);
-            ListItem::new(content)
+            ];
+
+            if !due_text.is_empty() {
+                let left_len: usize = spans.iter().map(|s| s.content.len()).sum();
+                let pad = content_width.saturating_sub(left_len + due_text.len());
+                spans.push(Span::raw(" ".repeat(pad)));
+                spans.push(Span::styled(due_text, Style::default().fg(due_color)));
+            }
+
+            ListItem::new(Line::from(spans))
         })
         .collect();