fix(ios): can not open keyboard in editor (#11401)

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

blocksuite/affine/shared/src/services/virtual-keyboard-service.ts

@@ -2,11 +2,16 @@ import { createIdentifier } from '@blocksuite/global/di';
 import type { ReadonlySignal } from '@preact/signals-core';
 
 export interface VirtualKeyboardProvider {
-  show: () => void;
-  hide: () => void;
   readonly visible$: ReadonlySignal<boolean>;
   readonly height$: ReadonlySignal<number>;
 }
 
-export const VirtualKeyboardProvider =
-  createIdentifier<VirtualKeyboardProvider>('VirtualKeyboardProvider');
+export interface VirtualKeyboardProviderWithAction
+  extends VirtualKeyboardProvider {
+  show: () => void;
+  hide: () => void;
+}
+
+export const VirtualKeyboardProvider = createIdentifier<
+  VirtualKeyboardProvider | VirtualKeyboardProviderWithAction
+>('VirtualKeyboardProvider');