Add newsletter section — The Communiqué (§ 09)

[rastermanden]

Summary

• Adds § 09 — The Communiqué newsletter section before the footer
• Left column: dispatch archive with 3 past issues (newsletter.json)
• Right column: subscribe form with email + frequency preference; mock 900ms submission delay shows a stamped "Approved" confirmation with a generated BB·NL·XXXX reference number
• Adds "Communiqué" link to both the desktop nav and the burger menu (#newsletter anchor)

Test plan

• Section renders correctly on mobile (390px), tablet (768px), and desktop (1280px)
• Subscribe form validates email and disables inputs during submission
• Confirmation state shows stamp, reference number, and descriptive text after submit
• Burger menu includes "Communiqué" link and closes on tap
• Desktop nav includes "Communiqué" link
• All palette variants (Treasury, Midnight Vault, Foundry, Verdigris) render correctly

https://claude.ai/code/session_01Poi4ANCPUUkK3Pwa7S2coz