fix: ensure unique VPN port assignment

Updated the port assignment logic to guarantee that a newly assigned port is unique by avoiding conflicts with existing port assignments. This addresses potential issues with port collisions that could disrupt VPN operations.

coldbrew/vpn/models.py

@@ -33,8 +33,11 @@ class VPN(models.Model):
 
         self.public_key = get_public_key(self.private_key)
 
-        if not self.port:
-            self.port = random.randint(10000, 40000)
+        while not self.port:
+            port = random.randint(10000, 40000)
+
+            if not VPN.objects.filter(port=port).exists():
+                self.port = port
 
         super().save(*args, **kwargs)