bug(settings): Make the mobile card span the viewport

[dschom]

Because

• The location/IP address container on the mobile "One last step to sync" screen renders narrower than the Figma spec on Android, with visible dead space either side.
• AppLayout gives <main> and <section> no width, so they shrink to fit their content and .card's own w-full never applies below mobileLandscape. No page-local change can widen a child past its card.

This pull request

• Spans <main> and <section> to the viewport below mobileLandscape, leaving shrink-to-fit in place above it.
• Updates the AppLayout snapshot for the new main class list.

Issue that this pull request solves

Closes: FXA-14460

Checklist

Put an x in the boxes that apply

• 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.

How to review (Optional)

• Key files/areas to focus on:
• Suggested review order:
• Risky or complex parts:

Screenshots (Optional)

Other information (Optional)

• AppLayout is shared, so this affects every non-split page below the 480px mobileLandscape breakpoint. Only cards whose content is narrower than the viewport change — measured geometry is identical at 480px and above.
• The split-layout branch already rendered full-bleed at phone widths; this brings the non-split branch in line with it.
• Out of scope: the Figma board's other note that Supplicant screens should have a white background on mobile.