feat: Extract Developer Portal as standalone Next.js app on port 3006

SDK customers can now access the documentation publicly without login.
The portal runs independently from admin-v2 on https://macmini:3006/.

- New developer-portal/ app with 26 pages, 2 components
- Docker service + nginx SSL reverse proxy on port 3006
- All /developers/* routes remapped to /* in the new app
- admin-v2 developer pages remain unchanged

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

developer-portal/app/globals.css

@@ -0,0 +1,35 @@
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+/* Custom scrollbar */
+::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+::-webkit-scrollbar-track {
+  background: #f1f5f9;
+}
+
+::-webkit-scrollbar-thumb {
+  background: #cbd5e1;
+  border-radius: 4px;
+}
+
+::-webkit-scrollbar-thumb:hover {
+  background: #94a3b8;
+}
+
+/* Smooth transitions */
+* {
+  transition-property: background-color, border-color, color, fill, stroke;
+  transition-timing-function: cubic-bezier(0.4, 0, 0.2, 1);
+  transition-duration: 150ms;
+}
+
+/* Focus styles */
+*:focus-visible {
+  outline: 2px solid #0ea5e9;
+  outline-offset: 2px;
+}