Update all remaining cmux.dev references to cmux.com (#1721)

- Swift app: feedback API endpoint, docs URLs, changelog URL, CLI help
- PostHog proxy: r.cmux.dev -> r.cmux.com
- All 20 README files: docs and blog links
- Homebrew cask: homepage URL in update-homebrew workflow

Co-authored-by: Lawrence Chen <lawrencecchen@users.noreply.github.com>

web/app/[locale]/posthog.tsx

@@ -7,7 +7,7 @@ import { useEffect, Suspense } from "react";
 
 if (typeof window !== "undefined") {
   posthog.init("phc_opOVu7oFzR9wD3I6ZahFGOV2h3mqGpl5EHyQvmHciDP", {
-    api_host: "https://r.cmux.dev",
+    api_host: "https://r.cmux.com",
     ui_host: "https://us.posthog.com",
     person_profiles: "identified_only",
     capture_pageview: false,