Fix nftables query by using full path to nft binary

Use explicit path /run/current-system/sw/bin/nft to match sudoers
configuration. Previously using 'nft' without path was resolving to
wrong location and failing permission checks.

- Change from 'sudo nft' to 'sudo /run/current-system/sw/bin/nft'
- Matches sudoers entry for passwordless execution
- Update version to v0.1.255

agent/src/collectors/systemd.rs

@@ -915,7 +915,7 @@ impl SystemdCollector {
     /// Returns: (tcp_ports_string, udp_ports_string)
     fn get_nftables_open_ports(&self) -> (String, String) {
         let output = Command::new("timeout")
-            .args(&["3", "sudo", "nft", "list", "ruleset"])
+            .args(&["3", "sudo", "/run/current-system/sw/bin/nft", "list", "ruleset"])
             .output();
 
         let output = match output {