Use qualified_id to generate node status files

[pcolt]

See PR 144 in the FE Platform to see an example of the new graph.json with the qualified ids

[pogmat]

@pcolt, @mfranzon: behavior of BE for qualified_id in jsons.

Scenario	Action	Serialized to JSON	Available at Runtime	Notes
qualified_id present and unique	Use as-is	Yes	Yes	Normal case - user-provided ID used everywhere
qualified_id missing	Auto-generate <node_id>_auto_<counter>	No	Yes	Backward compatible - warning logged, ID available for touch files/logs but transient
qualified_id duplicated	Throw DuplicateQualifiedIdException	N/A	N/A	Network loading fails with fatal error, main program terminates gracefully