feat: add API connection state management and update status display

src/app/state/misc.rs

@@ -240,6 +240,7 @@ pub struct MiscState {
     pub effort_level: usize,
     pub selected_index: usize,
     pub editor: Option<super::super::mode::editor::EditorState>,
+    pub api_connected: bool,
 }
 
 impl MiscState {
@@ -255,6 +256,7 @@ impl MiscState {
             effort_level: 1,
             selected_index: 0,
             editor: None,
+            api_connected: false,
         }
     }