fix(settings): wrap the scan-QR help link inside the phone frame

[dschom]

Because

• On the new pairing scan-QR page, long translations of the "Get help scanning" link (French, for one) overflow the phone graphic frame.

This pull request

• Caps the help link's width so long strings wrap onto a second line inside the phone screen.

Issue that this pull request solves

Closes: FXA-14486

Checklist

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• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).
• I have manually reviewed all AI generated code.

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Screenshots (Optional)

FXA-14486 — "Get help scanning" link, French, on /pair/authority/scan_qr

Storybook, Pages/Pair2/Authority/ScanQR, Firefox with locale fr. The local l10n bundle has no French for this key yet, so the link text is the string quoted in the ticket, placed into the link's text node. Link measures 220x42 px against the 46% cap of a 480 px card.

After (this branch)	After, denser QR

Other information (Optional)

• The overlay does not grow the card, so a translation needing a third line would still clip below the artwork. The French string fits in two.