feat: read org metadata from multiple graphs

[mburri]

cube creators can also be defined in https://lindas.admin.ch/fch/rvov

This PR adjusts the search cubes query to get creators from both graphs.
Unfortunatly, one uses dcterms:creator and the other schema:creator thats why an additional union was necessary:

 {
          ?iri dcterms:creator ?creatorIri .
        } UNION {
          ?iri schema:creator ?creatorIri .
        }

This took me quite some time to figure it out.

Currently, there are only cubes from the Federal Chancellery that use this graph for creators. I added the Federal Chancellery to the search spec (e2e) to verify that is shows up and the count is correct.

Without this change, e.g. currently on int or prod, there is no filter for the Federal Chancellery available.

---

• I added a CHANGELOG entry
• I made a self-review of my own code
• I wrote tests for the changes (if applicable)
• I wrote configurator and chart config migrations (if applicable)

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Project	Deployment	Actions	Updated (UTC)
visualization-tool	Ready	Preview, Comment	May 15, 2026 8:00am