feat(packages): add omniroute package

Add OmniRoute v3.8.28 - a unified AI router aggregating 160+ providers
with auto fallback, MCP/A2A support, and OpenAI-compatible APIs.

Uses a hybrid approach: GitHub source for dependency resolution via
fetchNpmDeps, combined with pre-built dist/ from the npm tarball to
avoid the complex Next.js build in the Nix sandbox.

packages/omniroute/default.nix

@@ -0,0 +1,5 @@
+{
+  pkgs,
+  ...
+}:
+pkgs.callPackage ./package.nix { }