Fix zoom on quantity input for iOS

[KaichenWang]

PR Summary:

Set quantity input font-size to 1.6rem (16px equivalent) to prevent iOS safari from zooming in on the input when focused.

Why are these changes introduced?

Fixes:

When you focus the qty field, there's a zoom that makes it harder to see the rest of the row (as well as the QTY rules popover) (from @vernalkick) Video 1 | Video 2

What approach did you take?

Set quantity input font-size to 1.6rem (16px equivalent) to prevent iOS safari from zooming in on the input when focused

Other considerations

Decision log

#	Decision	Alternatives	Rationale	Downsides
1	Increase quantity input font-size to 16px equivalent	Set meta tag viewport to include maximum-scale=1 or user-scalable=0	Safer from a11y perspective to increase font-size versus modifying viewport properties - MDN docs.	Increasing quantity input font-size may reduce the max number of digits displayed.

Visual impact on existing themes

Font-size for quantity inputs are increased.

Testing steps/scenarios

• Visually inspect quantity inputs

Demo links

• Store
• Editor

Checklist

• Added PR summary for release notes
• Requested review from UX (Only for changes that are affecting the experience or perceivable visual details)
• Created a ticket for the help.shopify.com documentation team about updates to theme settings. (Internal-only task)
• Followed theme code principles
• Linted with Theme Check
• Tested on mobile
• Tested on multiple browsers
• Tested for accessibility

[kmeleta]

👍 Interesting, never noticed that before