Release v0.5.0

[juancobo]

Federation and authorities release.

• Federations: tenants grouped into federations sharing one authority space (entities, places, and controlled vocabularies at federation scope), with steward-gated curation and federation-level publishing.
• Authorities module: merge and split workbenches with linked-description context cards, an append-only operations ledger with per-record history, duplicates worklists, places map explorer with coordinate editing and a controlled precision vocabulary, the combined places surface, redesigned authority record pages, notes fields, entities list filters, and the fully grouped and labelled role vocabulary.

Full details in the CHANGELOG's 0.5.0 section. Version bumped to 0.5.0; MAPTILER_KEY ships as an empty placeholder (see README setup).

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