paper-board ADRs

Architectural Decision Records for paper-board. All ADRs are public and canonical.

ADR	Topic
0001	Multi-repo microservices topology
0002	Postgres schema per service
0003	No cross-schema foreign keys
0004	Migrator as shared library (sdk/migrator)
0005	REST public + gRPC internal
0006	Vertical (tracer-bullet) implementation
0007	Repo naming + Helm chart conventions
0008	License, Code of Conduct, commit conventions
0009	Product-first phase ordering
0010	Standard Go service architecture
0011	Engineering-standards refresh policy
0012	End-to-end auth flow