Migrate remaining schema consumers to useGraphSchema and styled atoms

## Description

After the Cytoscape layer (#1725, #1726) and styling panels (#1727) are migrated, the remaining consumers of `mergedConfigurationSelector` and `useConfiguration()` need to switch to `useGraphSchema()` and the new styled type atoms.

Remaining consumers include: DataExplorer, SearchSidebar, SchemaGraph, EntitiesFilter, ConnectionDetail, ExportGraphButton, UserPrefixes, and the main GraphExplorer layout.

## Preferred Solution

- Components that need schema data (type names, attributes) use `useGraphSchema()`
- Components that need styled type info use `styledVertexTypeAtom(type)` / `styledEdgeTypeAtom(type)`
- Components that need preference data directly continue using `vertexPreferenceByTypeAtom(type)` / `edgePreferenceByTypeAtom(type)`
- Migrate incrementally — each module can be its own commit

## Related Issues

- Part of #1677
- Depends on #1725

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