feat(site): integration logos drift behind the landing swarm

[barockok]

What

• Swarm engine gains an opt-in logos list (+ logoZone): the big ambient shapes become full-colour integration logos — upright, no tumble, slow 2D drift with depth parallax, no glow, alpha ≤ 0.7. Without the option the engine is unchanged, so the portal login keeps today's look.
• The site build writes every integration's logo to _site/logos/ and passes the list into the hero; on wide layouts the logos live in the right/upper band ([0.46, 1, 0, 0.72]) so they never cross the headline, the lede, or the CTA row. Narrow layouts keep ambient off.

Verified

• Brand 45/45 (+3 skipped PNG cases), site 15/15, portal 173/173 unchanged; blip check 0.7 %.
• Screenshots at 1440×900 with the pointer left and right: copy and CTA clear, mark untouched, logos readable.