feat(legal): add /policies, /contact, /promotions for Stripe verification

Adds the consolidated Customer Policies doc covering customer service contact,
return / refund / dispute policy, cancellation policy, U.S. legal and export
restrictions, and promotional terms. Companion /contact page surfaces the
business phone (470) 949-4131 alongside the support/sales/billing/security
inboxes and target response SLAs. /promotions page exists as a stub so the
cross-reference in Policies §6.2 is live; it states no promotions are
currently active and will be appended to when offers run.

Refresh Privacy and Terms footers to point at /contact + /policies and drop
the stale hello@ mailto. Landing footer now exposes Privacy / Terms /
Policies / Contact links so Stripe's site review can reach them in one hop
from the marketing surface.

Mailing address is deferred until a P.O. Box is set up — left as an
in-source TODO and displayed publicly as "available on request" so we
don't ship a placeholder address.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/pages/LandingPage.tsx

@@ -429,7 +429,8 @@ export default function LandingPage() {
               <ul className="landing-footer-links">
                 <li><Link to="/privacy">Privacy</Link></li>
                 <li><Link to="/terms">Terms</Link></li>
-                <li><a href="mailto:hello@resolutionflow.com">Contact</a></li>
+                <li><Link to="/policies">Policies</Link></li>
+                <li><Link to="/contact">Contact</Link></li>
               </ul>
             </div>
           </footer>