feat(tui): add usage overlay and sidebar for displaying usage statistics and tasks

feat(tui): implement status bar with connection and turn state indicators
feat(tui): create workflow panel for agent status and progress visualization
feat(web): introduce web frontend interface with static file serving
feat(ws): add WebSocket interface for real-time communication and session management

apps/interfaces/tui/src/view/overlays/loading.rs

@@ -0,0 +1,28 @@
+//! Overlay: loading / processing spinner — shown during blocking operations.
+use ratatui::style::{Modifier, Style};
+use ratatui::text::Span;
+use ratatui::widgets::{Block, Paragraph};
+use ratatui::Frame;
+use crate::view::theme::Theme;
+
+/// Render the Loading overlay.
+pub fn render(
+    frame: &mut Frame,
+    area: ratatui::layout::Rect,
+    block: Block<'static>,
+    state: &crate::state::AppStateRest,
+) {
+    let block = block
+        .title(Span::styled(
+            " Loading ",
+            Style::default()
+                .fg(Theme::WARNING)
+                .add_modifier(Modifier::BOLD),
+        ))
+        .border_style(Style::default().fg(Theme::WARNING));
+    let spinner = ["⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"];
+    let frame_idx = (state.misc.tick_count as usize) % spinner.len();
+    let content = format!("  {} Processing, please wait...", spinner[frame_idx]);
+    let paragraph = Paragraph::new(content).block(block);
+    frame.render_widget(paragraph, area);
+}