Assist dialog: text field focus issues

**iOS device model, version and app version**

Model Name: iPhone 15 Pro
Software Version: iOS 17.5.1
App version: 2024.6 (2024.693)

**Home Assistant Core Version**

**Describe the bug**
First issue - when initially opening Assist dialog, you cannot immediately type a prompt as there's no focus in the text field.

Second issue - text field loses focus after pressing return key to send. This makes it a little bit more annoying to send additional follow up prompts as you can't just type, you've gotta click/tap or use tab key to get back into the text field. (Note: If you press the send button to right of text field instead, focus is retained as expected. It's only when sending using keyboard that focus gets lost.)

**To Reproduce**
1. Open Assist dialog, no focus initially (issue 1)
2. Type the word "test" and press return on iOS or Mac keyboard to send it. Text field loses focus after sending (issue 2). You can't just type another prompt into the text field cause it no longer has focus.

**Expected behavior**
1. Focus on text field when initially opening dialog so you can quickly type prompt
2. Keep focus in text field so that follow up / additional messages can be sent

Both of these work as expected in Safari, it's just the native assist dialog that behavior slightly differs

**Screenshots**

**Additional context**