Scaleway Flexible IPs are not linked to instances

## Scaleway Flexible IPs are not linked to instances ### Expected behavior When a Scaleway Flexible IP is attached to an instance, Cartography should create: ```cypher (:ScalewayFlexibleIp)-[:IDENTIFIES]->(:ScalewayInstance) ``` This relationship is declared by `ScalewayInstanceToFlexibleIpRel` and is already included in the Scaleway schema documentation. ### Actual behavior `ScalewayInstanceToFlexibleIpRel` is defined in `cartography/models/scaleway/instance/instance.py`, but `ScalewayInstanceSchema.other_relationships` only contains `ScalewayInstanceToVolumeRel`. `cartography.intel.scaleway.instances.instances.load_instances()` loads `ScalewayInstanceSchema`, so the `IDENTIFIES` relationship is never processed. The Flexible IP sync loads only `ScalewayFlexibleIpSchema`, which contains the project relationship but no instance relationship. The existing integration test checks project and volume relationships, but does not assert the Flexible IP relationship. ### To Reproduce 1. Sync a Scaleway project containing an instance with an attached Flexible IP. 2. Run: ```cypher MATCH (ip:ScalewayFlexibleIp)-[:IDENTIFIES]->(instance:ScalewayInstance) RETURN ip.id, instance.id ``` 3. Observe that no relationship is returned. ### Proposed fix - Add `ScalewayInstanceToFlexibleIpRel()` to `ScalewayInstanceSchema.other_relationships`. - Extend the Scaleway instance integration fixture and test to create a Flexible IP node and assert the `IDENTIFIES` relationship. ### Please complete the following information: - Cartography commit: `7c11f10c7fdb78420d337f910a050d366eded8cb` - Python version: Not environment-specific - OS: Not environment-specific ### Additional context The original Scaleway PR, #1645, declared this relationship. PR #2981 later re-enabled Flexible IP ingestion and reported live verification, but did not register the relationship in `ScalewayInstanceSchema` or add an integration assertion for it.