Replace literal-glyph UI icons in the URL preview cards with folds
Icon/Icons components, and hoist hardcoded provider brand hex values
into a single named BRAND_COLORS map.
Glyph -> folds icon:
- TikTok/Spotify musical note (♫) -> Icons.VolumeHigh
- Portrait play button (▶) -> Icons.Play
- Reddit comment count (💬) -> Icons.Message
- Steam gear (⚙) -> Icons.Setting
All use size="Inherit" so they keep the surrounding font-size/color.
Brand hex now referenced via BRAND_COLORS (tiktok, spotify, steam,
twitch, reddit, discord, npm, stackOverflow) instead of scattered
literals; colors are byte-for-byte identical and remain fixed brand
identities (not converted to TDS theme vars).
The game controller glyph (🎮) is left as-is: folds has no game/
controller icon and no close semantic match.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>