Add local and NetBox server notes and improve reliability

internal/cache/cache.go

@@ -2,6 +2,7 @@ package cache
 
 import (
 	"encoding/json"
+	"git.zb-server.de/Sebi/ssh-netbox-wrapper/internal/storage"
 	"os"
 	"path/filepath"
 	"sort"
@@ -116,12 +117,15 @@ func (c *Cache) Save() error {
 	if err != nil {
 		return err
 	}
-	return os.WriteFile(c.path, data, 0o644)
+	return storage.WriteFile(c.path, data, 0o600)
 }
 
 func (c *Cache) Upsert(e Entry) {
 	e.CachedAt = time.Now()
 	c.mu.Lock()
+	if old, ok := c.entries[e.Name]; ok && e.LastUsed.IsZero() {
+		e.LastUsed = old.LastUsed
+	}
 	c.entries[e.Name] = e
 	c.mu.Unlock()
 }