chore(database): add internal schema contract and builder foundation

[ditadi]

Summary

This PR adds the first AppKit-side foundation for the database plugin.

The broader database plugin goal is to give AppKit apps a typed, Lakebase-backed database lifecycle: developers declare tables in TypeScript, AppKit derives runtime/query metadata from that schema, and later stack layers use the same contract for DDL, migrations, type generation, and DML-only runtime access.

This PR specifically:

• Adds the database contract types used by the runtime/query layer: column metadata, relation metadata, filter operators, and wire limits.
• Adds defineSchema(...), table/column builders, FK refs, private/owner column markers, and Drizzle-backed engine table handles.
• Resolves FK-derived relations in one pass, including forward toOne and inferred reverse toMany relations.
• Derives Zod insert/update schemas from table metadata.
• Adds unit coverage for contract serialization, schema building, FK handling, relation inference, engine relation generation, private columns, and validators.

Scope

This is the schema/contract foundation only. It does not add the database plugin runtime, lifecycle CLI commands, migrations, grants, or deploy orchestration; those are layered in later PRs in the stack.

Tests

• Unit tests added under packages/appkit/src/database/**/tests.

[github-actions]

📦 Bundle size report

Compared against bundle-size-baseline.json (main).

@databricks/appkit

npm tarball (packed): 663 KB (+16 B) — gzipped download (dist + bin; excludes release-only docs/NOTICE).

dist	raw	gzip
JS (runtime)	689 KB	241 KB
Type declarations	268 KB	91 KB
Source maps	1.3 MB	448 KB
Other	11 KB	3.7 KB
Total	2.3 MB	784 KB

Per-entry composition (own code — deps external (as shipped))

Entry	Initial (gz)	Lazy (gz)	Total (gz)	node_modules (min)	Own code (min)
.	74 KB	2.5 KB	76 KB	external	244 KB
./beta	39 KB	231 B	39 KB	external	117 KB
./type-generator	19 KB	0 B	19 KB	external	54 KB

Chunks:

Entry	Chunk	Load	Size (gz)
.	index.js	initial	70 KB
.	utils.js	initial	4.0 KB
.	remote-tunnel-manager.js	lazy	2.5 KB
./beta	beta.js	initial	30 KB
./beta	databricks.js	initial	5.7 KB
./beta	service-context.js	initial	3.0 KB
./beta	client-options.js	initial	219 B
./beta	databricks.js	lazy	128 B
./beta	index.js	lazy	103 B
./type-generator	index.js	initial	19 KB

@databricks/appkit-ui

npm tarball (packed): 297 KB — gzipped download (dist + bin; excludes release-only docs/NOTICE).

dist	raw	gzip
JS (runtime)	363 KB	120 KB
Type declarations	203 KB	73 KB
Source maps	672 KB	219 KB
CSS	16 KB	3.3 KB
Total	1.2 MB	415 KB

Per-entry composition (consumer bundle — deps bundled, peerDeps external)

Entry	Initial (gz)	Lazy (gz)	Total (gz)	node_modules (min)	Own code (min)
./js	4.2 KB	49 KB	54 KB	208 KB	11 KB
./js/beta	20 B	0 B	20 B	0 B	0 B
./react	591 KB	49 KB	640 KB	1.8 MB	167 KB
./react/beta	20 B	0 B	20 B	0 B	0 B

Chunks:

Entry	Chunk	Load	Size (gz)
./js	index.js	initial	4.1 KB
./js	chunk	initial	120 B
./js	apache-arrow	lazy	49 KB
./js/beta	beta.js	initial	20 B
./react	index.js	initial	589 KB
./react	tslib	initial	2.1 KB
./react	apache-arrow	lazy	49 KB
./react/beta	beta.js	initial	20 B