revert(explore): use real client favicons (keep witchsky override)
Drop the four hand-built SVG client icons and go back to the per-client
favicon-from-source approach (Google S2 favicon CDN), so each client
shows its own real mark — bsky.app, blacksky.community, anisota.net,
deer.social. Witchsky stays on the locally-hosted PNG the user supplied
because witchsky.app's served favicon isn't a clean mark.
The 'Open on <client>' button on profile detail pages and the picker
inside the create/manage form both render each favicon on a small
white rounded chip, so the varied per-client colors sit cleanly
against the Atmosphere blue button background and don't look jarring.
Made-with: Cursor