chore: rename brand to "Reachy Mini Vibe Coding Apps"

feat(signin): swap reachy-head svg for hacker png illustration

style(signin): bump hero to 88px and add breathing room before title

style(signin): shrink reachy-head hero to 72px

style(signin): outlined CTA + smaller reachy-head illustration

feat(signin): use reachy-head + real HF logo and brand colors

feat(ui): Reachy head logo + awake illustration on signin

feat: initial Reachy Mini Vibe Coder space