feat: cherry-pick PR #183 — multi-provider support, PWA, dynamic models, UI improvements

Cherry-picked from decolua/9router PR #183.
Note: open-sse changes included but need further review due to extensive modifications.

Co-authored-by: Cursor <cursoragent@cursor.com>

next.config.mjs

@@ -4,9 +4,7 @@ const nextConfig = {
   images: {
     unoptimized: true
   },
-  env: {
-    NEXT_PUBLIC_CLOUD_URL: "https://9router.com",
-  },
+  env: {},
   webpack: (config, { isServer }) => {
     // Ignore fs/path modules in browser bundle
     if (!isServer) {