New brand mark & site footer

[JSONbored]

Problem: No LoopOver visual identity exists yet, and the site footer component still carries the old brand's mark and copy.

Area: Design / Frontend

Proposal: Produce a LoopOver logo/mark and update the site footer component, favicon, and social-preview (Open Graph) image to match.

Deliverables:

• Logo asset(s) in the formats the site needs (favicon, header/footer mark, OG image).
• Updated footer component reflecting the new brand.

Acceptance criteria:

• New mark renders correctly in the header, footer, and favicon.
• Social-share preview shows the new mark and copy.
• Renders correctly in both light and dark themes.

Test scenarios:

• Visual check across desktop and mobile viewport widths.
• Toggle light/dark theme and confirm the mark stays legible in both.
• Preview a shared link in a social-card debugger.

Resources:

• The site footer component in the UI app's site-chrome directory.

Boundaries:

• This depends on an actual design asset existing — if no mark is available yet, flag that explicitly rather than shipping a placeholder silently.

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Part of #4761.

[linear-code]

JSO-3436