feat: move node-type-registry to graphql/ and update for blueprint redesign

- Move node-type-registry from graphile/ to graphql/ folder
- Remove 'ref' field from BlueprintTable (table_name IS the identifier)
- Add optional 'schema_name' to BlueprintTable, BlueprintIndex, BlueprintFullTextSearch
- Rename source_ref/target_ref to source_table/target_table in BlueprintRelation
- Add optional source_schema_name/target_schema_name to BlueprintRelation
- Add BlueprintUniqueConstraint type (table_name, columns[], optional schema_name)
- Add unique_constraints[] to BlueprintDefinition
- Update codegen (generate-types.ts) to produce the new shapes
- Update generated blueprint-types.generated.ts to match
- Update README with new example (no ref, uses table_name directly)
- Update all path references from graphile/ to graphql/

Corresponds to constructive-db PR #721 which implements the server-side
blueprint redesign (remove refs, add table_name+schema_name resolution,
extract construction state, add unique_constraints phase).

Author: pyramation