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>

src/app/manifest.js

@@ -0,0 +1,30 @@
+export default function manifest() {
+  return {
+    name: '9Router - AI Infrastructure Management',
+    short_name: '9Router',
+    description: 'One endpoint for all your AI providers. Manage keys, monitor usage, and scale effortlessly.',
+    start_url: '/',
+    display: 'standalone',
+    background_color: '#0a0a0a',
+    theme_color: '#0a0a0a',
+    orientation: 'portrait-primary',
+    icons: [
+      {
+        src: '/icons/icon-192.svg',
+        sizes: '192x192',
+        type: 'image/svg+xml',
+      },
+      {
+        src: '/icons/icon-512.svg',
+        sizes: '512x512',
+        type: 'image/svg+xml',
+      },
+      {
+        src: '/icons/icon-512.svg',
+        sizes: '512x512',
+        type: 'image/svg+xml',
+        purpose: 'maskable',
+      },
+    ],
+  }
+}