feat(admin-web): add web/admin to repo

Initial commit of the Super-Admin web panel (Next.js + TypeScript).
CI admin-web-check job was failing because the directory was never
tracked in git.

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

web/admin/postcss.config.mjs

@@ -0,0 +1,9 @@
+/** @type {import('postcss-load-config').Config} */
+const config = {
+  plugins: {
+    tailwindcss: {},
+    autoprefixer: {},
+  },
+};
+
+export default config;