Use nfs-backup.toml and support completed status

Update agent to read nfs-backup.toml instead of legacy backup-status-*.toml
files. Add support for 'completed' status string used by backup script.

Changes:
- Read nfs-backup.toml from status directory
- Match 'completed' status as Status::Ok
- Simplify file scanning logic for single NFS backup file

agent/src/collectors/backup.rs

@@ -21,7 +21,7 @@ impl BackupCollector {
         }
     }
 
-    /// Scan directory for all backup status files
+    /// Scan directory for backup status file (nfs-backup.toml)
     async fn scan_status_files(&self) -> Result<Vec<PathBuf>, CollectorError> {
         let status_path = Path::new(&self.status_dir);
 
@@ -30,30 +30,15 @@ impl BackupCollector {
             return Ok(Vec::new());
         }
 
-        let mut status_files = Vec::new();
-
-        match fs::read_dir(status_path) {
-            Ok(entries) => {
-                for entry in entries {
-                    if let Ok(entry) = entry {
-                        let path = entry.path();
-                        if path.is_file() {
-                            if let Some(filename) = path.file_name().and_then(|n| n.to_str()) {
-                                if filename.starts_with("backup-status-") && filename.ends_with(".toml") {
-                                    status_files.push(path);
-                                }
-                            }
-                        }
-                    }
-                }
-            }
-            Err(e) => {
-                warn!("Failed to read backup status directory: {}", e);
-                return Ok(Vec::new());
-            }
+        // Look for nfs-backup.toml (new NFS-based backup)
+        let nfs_backup_file = status_path.join("nfs-backup.toml");
+        if nfs_backup_file.exists() {
+            return Ok(vec![nfs_backup_file]);
         }
 
-        Ok(status_files)
+        // No backup status file found
+        debug!("No nfs-backup.toml found in {}", self.status_dir);
+        Ok(Vec::new())
     }
 
     /// Read a single backup status file
@@ -76,7 +61,7 @@ impl BackupCollector {
     /// Calculate backup status from TOML status field
     fn calculate_backup_status(status_str: &str) -> Status {
         match status_str.to_lowercase().as_str() {
-            "success" => Status::Ok,
+            "success" | "completed" => Status::Ok,
             "warning" => Status::Warning,
             "failed" | "error" => Status::Critical,
             _ => Status::Unknown,