Close [BS-2917](https://linear.app/affine-design/issue/BS-2917/【移动端】ios-唤起键盘的edge-case)
This PR fixes an issue where the keyboard cannot be re-triggered on iOS devices after the keyboard toolbar is hidden or executing some actions in keyboard toolbar.
Key changes:
- Preserve and restore the initial input mode when keyboard toolbar shows/hides
- Improve virtual keyboard service interface to better handle keyboard state
- Add proper cleanup of input mode state in component lifecycle
L-Sun