Add entry and delete entry functionality with modals in TUI application

- Implemented add_entry method in HostsManager for adding new entries.
- Created AddEntryModal for user input when adding entries.
- Implemented delete_entry method in HostsManager for removing entries.
- Created DeleteConfirmationModal for user confirmation before deletion.
- Integrated modals into HostsManagerApp for adding and deleting entries.
- Added search functionality with SearchModal for finding entries by hostname or IP address.
- Updated keybindings to include shortcuts for adding and deleting entries.
- Added HelpModal to provide keyboard shortcuts and usage information.

tests/test_main.py

@@ -324,14 +324,17 @@ class TestHostsManagerApp:
             patch("hosts.tui.app.Config", return_value=mock_config),
         ):
             app = HostsManagerApp()
-            app.update_status = Mock()
+            app.push_screen = Mock()
 
             app.action_help()
 
-            # Should update status with help message
-            app.update_status.assert_called_once()
-            call_args = app.update_status.call_args[0][0]
-            assert "Help:" in call_args
+            # Should push the help modal screen
+            app.push_screen.assert_called_once()
+            # Verify the modal is a HelpModal instance
+            from hosts.tui.help_modal import HelpModal
+
+            args = app.push_screen.call_args[0]
+            assert isinstance(args[0], HelpModal)
 
     def test_action_config(self):
         """Test config action opens modal."""