epic(erd): read a schema as well as in dbdiagram (viewing only) #1286

Goal

Reading a database through its ER diagram should be as good as in dbdiagram: an arrangement that stays, tables that are easy to tell apart, columns that say what they are, relationships whose kind is visible, and a way to organise and annotate a large schema.

Viewing only. The diagram reflects the live database; no DBML editor and no schema editing. Layouts, colours, groups, notes and views are Querya's local data; nothing is written to the user's database.

Stage 1: stop it feeling unfinished

• feat(erd): the diagram keeps its layout: positions, collapsed and hidden tables, detail level, viewport #1275 the diagram keeps its layout (positions, collapsed / hidden tables, detail level, viewport)
• ui(erd): cards sized to their content, header colour by schema or chosen per table #1276 cards sized to their content, header colour by schema or per table
• feat(erd): column markers for unique, not null, default and identity #1277 column markers: unique, not null, default, identity
• feat(erd): detail levels on the toolbar: names, keys, all fields #1278 detail levels on the toolbar: names, keys, all

Stage 2: say more about the schema

• feat(erd): table and column comments from the database as notes #1279 table and column comments from the database as notes
• feat(erd): enum values on enum columns #1280 enum values on enum columns
• feat(erd): one-to-one and many-to-many, 1 / * end labels, select a relationship #1281 one-to-one and many-to-many, 1 / * end labels, select a relationship

Stage 3: organise large schemas

• feat(erd): table groups: by schema and user-defined, with a coloured frame #1282 table groups (by schema and user-defined)
• feat(erd): sticky notes on the canvas #1283 sticky notes on the canvas
• feat(erd): saved diagram views per connection #1284 saved diagram views
• feat(export): DBML and PDF export of the diagram #1285 DBML and PDF export

Model and storage

ErdTable gains schema and comment; ErdColumn gains unique, default, identity, comment, enum values; the catalog queries for PostgreSQL, MySQL and SQLite read them. A new LocalDb table holds the per-connection / database / schema layout (#1275), which later carries colours, groups, notes and views.

Out of scope

A DBML code editor next to the diagram, and editing the schema from the diagram.

References

• DBML docs, Enrichment & Visualization, Diagram detail levels, Table groups, Sticky notes
• Earlier ERD work: feat(erd): layered layout, orthogonal edges around tables and draggable cards #1145, refactor(erd): ErdSource per connection, schema-aware catalog, neighbourhood load #1147, feat(erd): Relations view in the table browser #1149, fix(erd): long column types overflow the card, PK+FK shows only PK, colour/font literals #1152–ui(erd): toolbar, Export menu and empty/error states per UI kit #1157, epic(viz): ER diagram, charts and plans: correct on real data, consistent with the UI kit #1166–perf(erd): hover rebuilds and repaints the whole canvas; no viewport culling; first layout on the UI thread #1169