feat: SaaS closed beta waitlist section

Gauges B2B interest in a commercial tier built on top of Greywall's
open-source core. The plugin SDK angle leans into what people have
actually been asking for: extending Greyproxy with custom heuristics,
Model Council, and token-saving MITM plugins. Web3forms handles signup.

Core stays free and open source; the new tier rides on top.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

components/hero.tsx

@@ -37,6 +37,15 @@ export function Hero() {
             <img src="https://img.shields.io/badge/Product%20Hunt-Greywall-D95E2A?style=flat&logo=producthunt&logoColor=white&labelColor=161614" alt="Product Hunt" className="h-5" />
           </a>
         </div>
+        <div className="mt-8 flex justify-center">
+          <a
+            href="#waitlist"
+            className="inline-flex items-center gap-2 px-5 py-2.5 rounded-md bg-primary text-primary-foreground font-sans text-sm font-medium hover:bg-primary/90 transition-colors"
+          >
+            Join the SaaS beta
+            <span aria-hidden="true">&rarr;</span>
+          </a>
+        </div>
       </div>
     </section>
   )