Task: Define and implement entity view document type

Define and implement a new entity_view document type — a single org file that lists every artefact of a named entity across all projections and components, with proj: links to the artefacts and their codegen archetypes. The document makes it easy to navigate the full set of related files and to spot missing projections. Implement projects/modeling/currency.org as the first example.

• projects/modeling/currency.org exists with ID 2AB04A53-A90D-45E0-917A-F3B4ED604186 and #+type: entity_view.
• Document has sections: Codegen models, SQL, C++ Domain, C++ Repository, C++ Service, C++ Generator, C++ Messaging (Protocol / Eventing / Handler), Qt, Other projections, Tests, Related entities.
• Every section has a table with proj: links to artefacts and their codegen archetypes.
• Hand-crafted artefacts are marked explicitly so completeness gaps are visible.
• Missing projections (e.g. domain entity model for currency) are called out inline.

1. Write projects/modeling/currency.org using #+type: entity_view and sections per projection. Survey the codebase first (Explore agent over 176 currency files).
2. Mark hand-crafted vs. generated artefacts; note missing projections inline.
3. The full entity_view doc-type definition (codegen template, compass scaffold, doc_types entry) is deferred — captured in this task's * Notes and to be done separately.