feat: adicionar menu de páginas e Page Switcher (Ctrl+P)

- Nova barra de páginas no topo (3 linhas) com moldura
- Página Tasks: body com lista + detalhe (comportamento normal)
- Página Markdown: placeholder (preparado para Feature 3)
- Calendar sempre visível no fundo, Tab cycle mantido
- Ctrl+P abre Page Switcher popup (navegação com ↑/↓/Enter/Esc)
- Enum Page: Tasks, Markdown
- Page::Markdown já funcional no switch mas sem preview real

src/app.rs

@@ -10,7 +10,7 @@ use tokio::sync::mpsc;
 use crate::domain::models::*;
 use crate::infrastructure::api::ApiClient;
 use crate::infrastructure::db::Db;
-use crate::ui::{Focus, NetworkStatus, Popup};
+use crate::ui::{Focus, NetworkStatus, Page, Popup};
 
 #[derive(Debug, Clone, Default)]
 pub struct SyncStats {
@@ -22,6 +22,7 @@ pub struct SyncStats {
 }
 
 pub struct App {
+    pub current_page: Page,
     pub lists: Vec<TaskList>,
     pub tasks: Vec<Task>,
     pub calendar_events: Vec<CalendarEvent>,
@@ -58,6 +59,7 @@ pub struct App {
     pub bulk_action_selected: usize,
     pub popup_list_indices: Vec<(String, String)>,
     pub popup_list_selected: usize,
+    pub page_switcher_selected: usize,
     auth_tx: std_mpsc::Sender<AuthEvent>,
     auth_rx: std_mpsc::Receiver<AuthEvent>,
     sync_tx: mpsc::Sender<SyncCommand>,
@@ -100,6 +102,7 @@ impl App {
         sort_tasks(&mut tasks);
 
         Self {
+            current_page: Page::Tasks,
             lists,
             tasks,
             calendar_events: Vec::new(),
@@ -135,6 +138,7 @@ impl App {
             bulk_action_selected: 0,
             popup_list_indices: Vec::new(),
             popup_list_selected: 0,
+            page_switcher_selected: 0,
             auth_tx,
             auth_rx,
             sync_tx,
@@ -329,6 +333,15 @@ impl App {
             return;
         }
 
+        if key.code == KeyCode::Char('p') && key.modifiers.contains(KeyModifiers::CONTROL) {
+            self.page_switcher_selected = match self.current_page {
+                Page::Tasks => 0,
+                Page::Markdown => 1,
+            };
+            self.show_popup = Some(Popup::PageSwitcher);
+            return;
+        }
+
         match key.code {
             KeyCode::Tab => {
                 match self.focus {
@@ -926,6 +939,27 @@ impl App {
                 }
                 _ => {}
             },
+            Popup::PageSwitcher => match key.code {
+                KeyCode::Esc => {
+                    self.show_popup = None;
+                }
+                KeyCode::Up => {
+                    self.page_switcher_selected = self.page_switcher_selected.saturating_sub(1);
+                }
+                KeyCode::Down => {
+                    if self.page_switcher_selected + 1 < 2 {
+                        self.page_switcher_selected += 1;
+                    }
+                }
+                KeyCode::Enter => {
+                    self.current_page = match self.page_switcher_selected {
+                        0 => Page::Tasks,
+                        _ => Page::Markdown,
+                    };
+                    self.show_popup = None;
+                }
+                _ => {}
+            },
         }
     }
 

src/main.rs

@@ -156,6 +156,7 @@ fn main() -> io::Result<()> {
             app.refresh_if_needed();
 
             let view = AppView {
+                current_page: &app.current_page,
                 lists: &app.lists,
                 tasks: &app.tasks,
                 calendar_events: &app.calendar_events,
@@ -181,6 +182,7 @@ fn main() -> io::Result<()> {
                 bulk_action_selected: app.bulk_action_selected,
                 popup_list_indices: &app.popup_list_indices,
                 popup_list_selected: app.popup_list_selected,
+                page_switcher_selected: app.page_switcher_selected,
             };
             draw(frame, view);
         })?;

src/ui/components.rs

@@ -10,7 +10,7 @@ use ratatui::Frame;
 
 use crate::domain::models::*;
 use crate::app::SyncStats;
-use super::NetworkStatus;
+use super::{NetworkStatus, Page};
 
 const FOCUS_COLOR: Color = Color::Yellow;
 const SELECTED_COLOR: Color = Color::Green;
@@ -39,6 +39,30 @@ fn relative_due_str(due: chrono::NaiveDateTime) -> (String, Color) {
     }
 }
 
+pub fn render_page_menu(frame: &mut Frame, area: Rect, current_page: &Page) {
+    let block = Block::default()
+        .borders(Borders::ALL)
+        .border_style(Style::default().fg(Color::DarkGray));
+
+    let inner = block.inner(area);
+    frame.render_widget(&block, area);
+
+    let active = current_page == &Page::Tasks;
+    let style = if active {
+        Style::default().fg(Color::Yellow).add_modifier(Modifier::BOLD)
+    } else {
+        Style::default().fg(Color::Cyan)
+    };
+
+    let text = Line::from(vec![
+        Span::raw(" "),
+        Span::styled(" Tasks ", style),
+    ]);
+
+    let paragraph = Paragraph::new(text);
+    frame.render_widget(paragraph, inner);
+}
+
 pub fn render_task_list(
     frame: &mut Frame,
     area: Rect,
@@ -642,6 +666,43 @@ pub fn render_pick_list_popup(
     frame.render_widget(paragraph, popup_area);
 }
 
+pub fn render_page_switcher_popup(frame: &mut Frame, area: Rect, selected: usize) {
+    let popup_area = centered_rect(50, 8, area);
+    frame.render_widget(Clear, popup_area);
+    let block = Block::default()
+        .borders(Borders::ALL)
+        .style(Style::default().bg(POPUP_BG))
+        .border_style(Style::default().fg(POPUP_BORDER))
+        .title(" Pages ")
+        .title_alignment(Alignment::Left);
+
+    let pages: [&str; 2] = ["Tasks", "Markdown"];
+
+    let mut lines = vec![Line::from("")];
+    for (i, title) in pages.iter().enumerate() {
+        let prefix = if i == selected { " > " } else { "   " };
+        let style = if i == selected {
+            Style::default().fg(FOCUS_COLOR).add_modifier(Modifier::BOLD)
+        } else {
+            Style::default().fg(Color::Cyan)
+        };
+        lines.push(Line::from(Span::styled(
+            format!("{}{}", prefix, title),
+            style,
+        )));
+    }
+    lines.push(Line::from(""));
+    lines.push(Line::from(Span::styled(
+        "  \u{2191}/\u{2193}: navigate  Enter:switch  Esc:cancel",
+        Style::default().fg(Color::DarkGray),
+    )));
+
+    let paragraph = Paragraph::new(Text::from(lines))
+        .block(block)
+        .alignment(Alignment::Left);
+    frame.render_widget(paragraph, popup_area);
+}
+
 pub fn render_device_auth_popup(
     frame: &mut Frame,
     area: Rect,

src/ui/mod.rs

@@ -2,7 +2,10 @@ pub mod components;
 
 use std::collections::BTreeSet;
 
-use ratatui::layout::{Constraint, Direction, Layout};
+use ratatui::layout::{Alignment, Constraint, Direction, Layout};
+use ratatui::style::{Color, Style};
+use ratatui::text::{Line, Span, Text};
+use ratatui::widgets::{Block, Borders, Paragraph};
 use ratatui::Frame;
 
 use crate::app::SyncStats;
@@ -16,6 +19,12 @@ pub enum Focus {
     Calendar,
 }
 
+#[derive(Debug, Clone, PartialEq)]
+pub enum Page {
+    Tasks,
+    Markdown,
+}
+
 #[derive(Debug, Clone, PartialEq)]
 pub enum Popup {
     Input,
@@ -24,6 +33,7 @@ pub enum Popup {
     ConfirmDelete { context: String },
     BulkAction,
     PickList,
+    PageSwitcher,
     DeviceAuth { url: String, code: String },
 }
 
@@ -35,6 +45,7 @@ pub enum NetworkStatus {
 }
 
 pub struct AppView<'a> {
+    pub current_page: &'a Page,
     pub lists: &'a [TaskList],
     pub tasks: &'a [Task],
     pub selected_list: usize,
@@ -60,6 +71,7 @@ pub struct AppView<'a> {
     pub bulk_action_selected: usize,
     pub popup_list_indices: &'a [(String, String)],
     pub popup_list_selected: usize,
+    pub page_switcher_selected: usize,
 }
 
 pub fn draw(frame: &mut Frame, view: AppView) {
@@ -68,43 +80,66 @@ pub fn draw(frame: &mut Frame, view: AppView) {
     let main_layout = Layout::default()
         .direction(Direction::Vertical)
         .constraints([
+            Constraint::Length(3),
             Constraint::Min(0),
             Constraint::Length(12),
             Constraint::Length(1),
         ])
         .split(area);
 
-    let body_area = main_layout[0];
+    let menu_area = main_layout[0];
-    let calendar_area = main_layout[1];
+    let body_area = main_layout[1];
-    let status_area = main_layout[2];
+    let calendar_area = main_layout[2];
+    let status_area = main_layout[3];
 
-    let body_layout = Layout::default()
+    render_page_menu(frame, menu_area, view.current_page);
-        .direction(Direction::Horizontal)
-        .constraints([Constraint::Percentage(50), Constraint::Percentage(50)])
-        .split(body_area);
 
-    let is_task_list_focused = view.focus == Focus::TaskList;
+    match view.current_page {
-    render_task_list(
+        Page::Tasks => {
-        frame,
+            let body_layout = Layout::default()
-        body_layout[0],
+                .direction(Direction::Horizontal)
-        view.lists,
+                .constraints([Constraint::Percentage(50), Constraint::Percentage(50)])
-        view.selected_list,
+                .split(body_area);
-        view.list_tabs_scroll,
-        view.tasks,
-        view.selected_task,
-        is_task_list_focused,
-        view.task_list_scroll,
-        view.selected_tasks,
-    );
 
-    let is_detail_focused = view.focus == Focus::Detail;
+            let is_task_list_focused = view.focus == Focus::TaskList;
-    render_detail(
+            render_task_list(
-        frame,
+                frame,
-        body_layout[1],
+                body_layout[0],
-        view.tasks.get(view.selected_task),
+                view.lists,
-        is_detail_focused,
+                view.selected_list,
-        view.detail_scroll,
+                view.list_tabs_scroll,
-    );
+                view.tasks,
+                view.selected_task,
+                is_task_list_focused,
+                view.task_list_scroll,
+                view.selected_tasks,
+            );
+
+            let is_detail_focused = view.focus == Focus::Detail;
+            render_detail(
+                frame,
+                body_layout[1],
+                view.tasks.get(view.selected_task),
+                is_detail_focused,
+                view.detail_scroll,
+            );
+        }
+        Page::Markdown => {
+            let block = Block::default()
+                .borders(Borders::ALL)
+                .border_style(Style::default().fg(Color::DarkGray))
+                .title(" Markdown ")
+                .title_alignment(Alignment::Left);
+            let text = Text::from(Line::from(Span::styled(
+                "Markdown preview coming soon",
+                Style::default().fg(Color::DarkGray),
+            )));
+            let paragraph = Paragraph::new(text)
+                .block(block)
+                .alignment(Alignment::Center);
+            frame.render_widget(paragraph, body_area);
+        }
+    }
 
     let is_calendar_focused = view.focus == Focus::Calendar;
     render_calendar_panel(
@@ -130,6 +165,7 @@ pub fn draw(frame: &mut Frame, view: AppView) {
             Popup::ConfirmDelete { context } => render_confirm_popup(frame, area, context),
             Popup::BulkAction => render_bulk_action_popup(frame, area, view.selected_tasks.len(), view.bulk_action_selected),
             Popup::PickList => render_pick_list_popup(frame, area, view.popup_list_indices, view.popup_list_selected),
+            Popup::PageSwitcher => render_page_switcher_popup(frame, area, view.page_switcher_selected),
             Popup::DeviceAuth { url, code } => render_device_auth_popup(frame, area, url, code, view.auth_error),
         }
     }