Curator tool: a supported Angular diagram library from this repo #349

Follow-up to the embeddable-diagram work (spec 009). Loop in the curator-tool owners before any change.

`reactome/curator-tool-frontend` (Angular 17, NgModules) renders diagrams through `ngx-reactome-diagram` 0.0.37 and `ngx-reactome-cytoscape-style` 0.0.20. Both are installed from local tarballs built in `ngx-reactome-base`, not from a registry. It reaches well past a viewer:

• `diagram.cy`, the raw cytoscape instance, for zoom, pan and editing;
• `displayNetwork(elements)`, a `network_displayed` DOM event, and `DiagramService`;
• deep imports of model types (`ngx-reactome-diagram/lib/model/diagram.model`);
• a `DIAGRAM_CONFIG_TOKEN` for its diagram URL;
• `[usedbId]` and `[blockRouterChange]` inputs.

So the embeddable web component in spec 009 (view-only, isolated from its host) isn't what the curator tool needs. It needs an Angular library: the diagram component and services published from this repo, with a deliberate public API that covers the editing hooks it uses today.

Questions for the owners before any design:

• Which of those hooks are still needed?
• Can it move from Angular 17 to the version this repo is on?
• Would a registry package (or a tarball built by this repo's CI) replace `ngx-reactome-base`?