docs: add project vision, MVP architecture spec, and reference material

- docs/VISION.md: product vision + feature catalogue (MVP / post-MVP / later)
- docs/specs/2026-06-02-mvp-architecture.md: MVP architecture + 16-entry decision log
- reference/: Spectrum 5.0 cataloguing + Riksantikvarieämbetet source material (build-time reference)
- CLAUDE.md: project guidance for Claude Code

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

reference/README.md

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+# Reference material
+
+Build-time reference material — prior art, definitions, and domain guidance we read
+while designing this collection management system (samlingsförvaltningssystem). These
+are durable, greppable source artifacts, **not** documentation of this project's own
+code. Each file carries a `source:` header with the original URL and retrieval date.
+
+## Riksantikvarieämbetet — "God praxis att välja samlingsförvaltningssystem"
+
+The Swedish National Heritage Board's (Riksantikvarieämbetet) guidance on choosing and
+introducing a collection management system. Fetched 2026-06-01 from
+<https://www.raa.se/museer/digital-omstallning-pa-museiomradet/om-digitalisering/god-praxis-att-valja-samlingsforvaltningssystem/>.
+Backed by the report *"God samlingsförvaltning: praxis för val och användning av
+samlingsförvaltningssystem"* (urn:nbn:se:raa:diva-6213). Content is in Swedish, kept verbatim.
+
+| File | Page |
+|------|------|
+| [raa-01-vad-och-varfor.md](raa-01-vad-och-varfor.md) | 1. Samlingsförvaltningssystem, vad och varför? |
+| [raa-02-vad-ar-inte.md](raa-02-vad-ar-inte.md) | 2. Vad är ett samlingsförvaltningssystem inte? |
+| [raa-03-overvaganden.md](raa-03-overvaganden.md) | 3. Överväganden vid val av samlingsförvaltningssystem |
+| [raa-04-vagkarta.md](raa-04-vagkarta.md) | 4. Vägkarta för val av samlingsförvaltningssystem |
+| [raa-05-spectrum-processerna.md](raa-05-spectrum-processerna.md) | 5. Spectrum-processerna och samlingsförvaltningssystem |
+| [raa-06-grundlaggande-tekniska-funktioner.md](raa-06-grundlaggande-tekniska-funktioner.md) | 6. Grundläggande tekniska funktioner |
+| [raa-07-datastandarder.md](raa-07-datastandarder.md) | 7. Datastandarder |
+| [raa-08-referenser-och-lankar.md](raa-08-referenser-och-lankar.md) | 8. Referenser och länkar (systems, vendors, literature) |
+| [raa-09-kravspecifikationstabell.md](raa-09-kravspecifikationstabell.md) | 9. Kravspecifikationstabell (CHIN CMSCC) |
+| [raa-10-fallstudie-jonkoping.md](raa-10-fallstudie-jonkoping.md) | Fallstudie: Jönköpings läns museum (Primus) |
+| [raa-11-fallstudie-thielska.md](raa-11-fallstudie-thielska.md) | Fallstudie: Thielska Galleriet (MuseumPlus) |
+
+## Collections Trust — Spectrum 5.0 (primary source)
+
+The actual standard, not just guidance about it. Transcribed from the official PDF.
+
+| File | Page |
+|------|------|
+| [spectrum-5.0-cataloguing.md](spectrum-5.0-cataloguing.md) | Cataloguing procedure — definition, scope, the Spectrum standard (policy questions + minimum requirements), suggested procedure, and the **full unit-of-information / field list** (the closest thing to a canonical object data model). License: Spectrum licence. |
+| [spectrum-5.0-cataloguing-units-of-information.md](spectrum-5.0-cataloguing-units-of-information.md) | **Data dictionary** for the above — every field with its constraint (term source / form of name / format / free text) and a link to its canonical Collections Trust definition page. The field-level reference for schema design. |
+
+### Key external standards referenced
+
+- **Spectrum 5.0** (Collections Trust) — the de-facto collection management standard; 21 procedures, 9 primary. <https://collectionstrust.org.uk/spectrum/>
+- **CIDOC CRM** (ISO 21127) — ontology for cultural heritage data structure. <https://www.cidoc-crm.org/>
+- **LIDO** — CIDOC-CRM-based exchange format.
+- **CHIN CMSCC** — Collections Management System Criteria Checklist (requirements list).
+- Vocabularies: Getty AAT/TGN/ULAN, KulturNav (Nordic), Wikidata, Iconclass.
+- Aggregators: K-samsök / Kringla, Europeana, Sveriges dataportal.