Bump graph schema contract to 2.0.0 and regenerate published artifacts #10

Prefixing the node labels and relationship types renames every element of the graph contract, which is a breaking change for existing consumers. The published contract version and artifacts must reflect this.

Bump SCHEMA_VERSION from 1.0.0 to 2.0.0, regenerate the machine-readable schema (schema.neo4j.json), and refresh the documentation (the README graph section and the --app-name help text) to the prefixed names. The conformance test must assert that the checked-in schema matches the catalog.