Accessibility improvements

[doubletaco]

Description

Improved the accessibility of some UI elements for people who use screen readers and voice control.

• Added missing accessible names to temperature decrement and increment buttons near the iron's temperature readout.
• Gave the SET temperature the "alert" role so the value will be read after it is incremented/decremented by screen readers
• Updated the section titles in the iron settings to have correct semantic roles and states. This follows the WAI-ARIA Authoring Practices Guide Disclosure Pattern
• Added accessible names to settings input elements by associating them programatically with their text labels.

Related Issues

N/A

Screenshots

N/A, all semantic changes.

Checklist

• [x] I have tested my changes locally and they work as expected.
• [x] I have updated the documentation, if applicable.
• [x] I have added appropriate tests, if applicable.
• [x] I have run the linter and fixed any issues, if applicable.

Other information

Tested using the NVDA and JAWS screen readers on Chrome Version 128.0.6613.138