Replaces the gold experiment with the actual brand.
- Palette: brand charcoal (#303030, sampled from the logo's own background)
with the logo's glow as the primary accent (#6d7cff) and its purple
(#c084fc) as a secondary. Text is the palette's white / light gray. Light
mode re-tuned to the same hues.
- Logo: the source mark keyed off its charcoal background to RGBA, cropped to
its content bounds, and added as web/public/logo.png. It now appears in the
sidebar and on the login screen; a square favicon is derived from it and
wired into index.html.
- The featured kicker uses the purple secondary, so both brand hues are present
without adding a second competing accent.
Verified: logo loads in the app, accent resolves to #6d7cff, secondary to
#c084fc, surface to #303030.
