fix(v4): update homepage mobile demo fallback images (#10810)

* fix(v4): update homepage mobile demo fallback images

Replace registry dashboard screenshots with compressed CardsDemo captures and narrow the mobile bleed width to 140vw.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(v4): remove container-wrapper padding on homepage

Use p-0 on the demo section wrapper so the mobile preview image aligns flush without extra horizontal inset.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(v4): drop redundant md:p-0 on homepage wrapper

Co-authored-by: Cursor <cursoragent@cursor.com>

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Co-authored-by: Cursor <cursoragent@cursor.com>