Add modular service configuration with SearXNG and Nginx

- Create modules/ directory with reusable NixOS modules
- Add system module for main user configuration
- Add podman module for rootless container support
- Add nginx module with automatic Let's Encrypt SSL
- Add searxng module with Anubis AI firewall protection
- Configure SearXNG at search.ashisgreat.xyz
- Enable nginx reverse proxy with HTTPS

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

modules/default.nix

@@ -0,0 +1,9 @@
+# Module exports
+{
+  imports = [
+    ./system.nix
+    ./podman.nix
+    ./nginx.nix
+    ./searxng.nix
+  ];
+}