bug: ion-datetime calendar part is blank (iOS 26.2)

### Prerequisites

- [x] I have read the [Contributing Guidelines](https://github.com/ionic-team/ionic-framework/blob/main/docs/CONTRIBUTING.md#creating-an-issue).
- [x] I agree to follow the [Code of Conduct](https://ionicframework.com/code-of-conduct).
- [x] I have searched for [existing issues](https://github.com/ionic-team/ionic-framework/issues) that already report this problem, without success.

### Ionic Framework Version

v7.x

### Current Behavior

This issue has only been seen and reproducible on ios 26.2 only.

When opening ion-datetime, more often than not, the calendar part is blank. This is because ion-datetime does NOT have the class 'datetime-ready', which it needs to show the calendar part.

### Expected Behavior

Opening ion-datetime displays the calendar part.

### Steps to Reproduce

1. Tap on an ion-datetime
2. Observe
NOTE: This does not happen every time. Higher chance to reproduce after launching an app.

### Code Reproduction URL

.

### Ionic Info

Ionic:

Ionic CLI : 7.1.1 (/usr/local/lib/node_modules/@ionic/cli)
Ionic Framework : @ionic/react 7.8.6

Capacitor:

Capacitor CLI : 7.4.3
@capacitor/android : 7.4.3
@capacitor/core : 7.4.3
@capacitor/ios : 7.4.3

Utility:

cordova-res : not installed globally
native-run : 2.0.1

System:

NodeJS : v20.19.5
npm : 10.8.2
OS : macOS Unknown (Sequoia Version 15.7.3 (24G419))

### Additional Information

https://github.com/user-attachments/assets/bb215654-6118-4bd8-b3cc-50d5666c5f58

Start by reproducing ion-datetime in an Ionic React app on iOS 26.2, especially after launching the app, and inspect when the datetime-ready class is absent. The issue is done when opening ion-datetime consistently displays the calendar part on the affected platform.

由索引模型根据 Issue 内容生成。