Fix openclaw config syntax - use external json file

- Move openclaw config to separate json file
- Reference file directly in podman module
- Remove problematic builtins.toJSON with nested arrays

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

modules/openclaw-podman.nix

@@ -47,7 +47,7 @@ in
         config.sops.templates."openclaw.env".path
       ];
       volumes = [
-        "${config.sops.templates."openclaw_config.json".path}:/root/.openclaw/config.json:ro"
+        "${./openclaw-config.json}:/root/.openclaw/config.json:ro"
         "openclaw-data:/root/.openclaw"
       ];
       extraOptions = [