Doc Add ER Diagram

When the SQL schema gains tables or relationships and the ER diagram at projects/ores.sql/modeling/ores_schema.puml needs to catch up, or when documenting newly-added tables.

1. Identify the tables. Read projects/ores.sql/create/*_create.sql to enumerate every table, its columns, primary key, foreign keys, and indexes.
2. Group entities into domain packages — IAM, RBAC, Assets, Variability, etc. The package colour palette is in the conventions doc.
3. Author the diagram following the conventions in PlantUML ER diagram conventions — skeleton, entity styling (<<temporal>> / <<junction>> / none), field notation, relationships, notes, temporal columns.

4. Validate via How do I generate PlantUML diagrams?:

   cmake --build --target generate_ores_schema_diagram
   

5. Self-check against the evaluation checklist in the conventions doc (every table represented, FK arrows match the SQL REFERENCES, stereotypes correct, packages logical, syntax valid).

• How do I generate PlantUML diagrams? — build / preview loop.

• PlantUML ER diagram conventions — styling and the evaluation checklist.
• ores.sql — the component whose schema this diagram documents.
• plantuml-class-modeler — sibling skill for class diagrams.