Desktop: Accessibility: Add missing labels to the note attachments screen and master password dialog

[personalizedrefrigerator]

Summary

This pull request adds labels to three items that did not previously have screen reader accessible text:

• The hide/show password button in the master password dialog.
• The valid/invalid checkmark in the master password dialog.
• The "reverse sort order" buttons in the note attachments screen.

Additionally, it:

• Associates label elements with password inputs using htmlFor and id.
• Marks invalid passwords in the master password dialog with aria-invalid.

Related: WCAG SC 1.1.1, SC 4.1.2.

Testing plan

Linux (Fedora 40):

1. Enable the Orca screen reader.
2. Start Joplin.
3. Open the note attachments screen.
4. Move keyboard focus to the "reverse sort order" button for "size".
5. Verify that Sort "size" in descending order is read by the screen reader.
6. Close the note attachments screen and open the master password dialog.
7. Move keyboard focus to the "show password" button.
8. Verify that "Show password, push button" is read by the screen reader.
9. Push the button.
10. Verify that the screen reader reads "Hide password".
11. Set a password if one isn't already set.
12. Re-open the master password dialog.
13. Click "Change master password".
14. Focus the "current password" input. Verify that the screen reader reads "current password, password, text" before reading the password length and whether it's selected.
15. Move focus to just after the "Current password" input. Verify that the screen reader reads "valid".
16. Change the current password so that it's invalid.
17. Move focus to just after the "Current password" input. Verify that the screen reader reads "invalid".