Ship the Runic Gateway emblem as the baked-in default favicon so an
instance renders a tab icon with no BRAND_FAVICON set, and place a
left-justified "Powered By" badge in the site footer.
- brand.favicon now defaults to /assets/img/favicon.ico (was empty).
BRAND_FAVICON still overrides per-instance.
- Add favicon.ico + powered-by.svg under client/public/assets/img.
- SiteFooter: badge pinned to the left of the centered content column
(absolute on >=641px, stacked on mobile); info text stays centered.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XmHdsbnLzDMAVQkAoTQSBe
