Sync brand mark stroke-width with updated icon.svg

The horizontal white crossroads line in app/icon.svg was tuned to a slightly thinner stroke-width (2.5 to 2.0). Propagated that same value to every other place the badge geometry is duplicated so all rendered instances stay visually identical.

Decisions

Treat app/icon.svg as the single source of truth for the badge geometry - regenerate the derived favicon.ico/apple-icon.png binaries and update the two React component copies (BrandMark, BrandSocialImage) from it rather than editing each independently.

Milestones

Regenerated app/favicon.ico and app/apple-icon.png from the updated SVG via the throwaway sharp-based generation script.
Updated the horizontal line stroke-width in components/brand/brand-mark.tsx and components/brand/brand-social-image.tsx to match.
Confirmed via the pinned Docker Playwright image that the change is within the existing visual regression baseline's tolerance - no baseline update required.

Validation

npm run typecheck
npm run lint
npm run build