Legal pages (Terms, Privacy, Disclaimer) + always-present footer

- New /terms, /privacy, /disclaimer pages in the site style with real content
  tailored to an on-chain ad+referral platform (no income guarantee, crypto
  risk, rehearsal note, privacy of email/wallet/profile, acceptable use).
- renderNav now appends a persistent footer with legal + site links on every
  public page; member-area sidebar gets a Legal link group.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/assets/legal.js

@@ -0,0 +1,2 @@
+// legal/static content pages: render the shared nav + footer
+(async function () { try { await IAP.renderNav(''); } catch (e) {} })();