feat: add lesson export and import functionality

- Implemented `LessonExport` and `LessonImport` actions in the action module.
- Added corresponding command parsing for lesson export and import.
- Created functions to handle lesson export and import in the memory module.
- Updated state management to reflect changes after lesson operations.
- Introduced deferred operations for handling asynchronous tasks in the event loop.
- Enhanced the tool execution context to include graduated checks for file operations.
- Added OAuth support with PKCE for secure authorization flows.
- Implemented a loopback server for handling OAuth redirects.
- Refactored various modules to improve code organization and maintainability.

src/app/mode/effort.rs

@@ -0,0 +1,14 @@
+use crate::app::state::rest::AppStateRest;
+
+pub const EFFORT_LEVELS: &[&str] = &["low", "medium", "high", "xhigh", "max"];
+
+pub fn current_effort(_state: &AppStateRest) -> usize {
+    1
+}
+
+pub fn cycle_effort(state: &mut AppStateRest) {
+    let current = current_effort(state);
+    let next = (current + 1) % EFFORT_LEVELS.len();
+    let _ = next;
+    state.dirty = true;
+}