feat(database): foundation — schema builder, plugin skeleton, connectors

[ditadi]

🥞 Stacked PR

Use this link to review incremental changes.

• stack/database/foundation [Files changed]
  • stack/database/server [Files changed]
    • stack/database/brownfield [Files changed]
      • stack/database/init [Files changed]
        • stack/database/frontend [Files changed]
          • stack/database/ui [Files changed]
            • stack/database/advanced [Files changed]
              • stack/database/release [Files changed]

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Overview

This is the first PR in the database plugin stack. It adds the foundation needed by the later server, CLI, frontend, and RLS layers, without introducing the full end-user workflow yet.

What changed

• Adds the beta database plugin skeleton, manifest, defaults, convention loader, and package exports.
• Adds defineSchema() plus typed column helpers for declaring AppKit-managed database schemas.
• Adds column metadata used by runtime validation, type generation, drift detection, and docs.
• Adds column.private() metadata so later layers can hide sensitive columns from default reads, routes, and generated UI.
• Adds Lakebase/PostgREST connector primitives and safer pool/shutdown behavior (statement_timeout, async drain, schema-load isolation, pool stats).

Review guidance

Start here before reviewing the rest of the stack. The main contract to validate is the schema-builder API and metadata shape, because downstream PRs consume it for route generation, introspection, browser types, and UI metadata.

Test plan

• Schema builder and column helper tests
• Plugin skeleton/config tests
• Pool drain and shutdown tests
• Full stack verification run locally before push