Migrate ORM database layer from Knex.js to Kysely

[ichiriac]

Summary
Migrate the NormalJS core database abstraction from Knex.js to Kysely for improved type-safety, modern query composition, and better TypeScript support.

Background

• Our current implementation relies on Knex.js for query building and connection management in src/Connection.js, src/Repository.js, and the model/query logic in src/Model.js, src/Record.js.
• Kysely offers superior type inference and stronger TS support, aligned with our goal for strict type coverage throughout the ORM.

Scope

• Replace all Knex imports/usages with Kysely equivalents in connection, transaction, and query builder subsystems.
• Refactor model definition patterns to leverage Kysely’s typed query features.
• Update Connection class to use Kysely clients (support for PostgreSQL/SQLite must be retained).
• Ensure the lazy loading mechanisms remain compatible and efficient with Kysely.
• Adjust repo.sync() logic to reflect differences in schema migration APIs.
• Adapt transaction management (repo.transaction()) for Kysely idioms.
• Validate relation patterns (one-to-many, many-to-many) work with Kysely’s approach.
• Update tests in integration/demo suites to cover the new query builder and ensure 80%+ coverage remains.

Acceptance Criteria

• All core modules rely on Kysely, with no residual Knex references.
• All tests passing (npm test) and coverage reports >= 80%.
• Demo projects (blog, crm, stocks) function correctly with Kysely.
• Document new architecture and developer setup in README/code comments.

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References:

• Kysely Documentation
• See architecture notes in README.md to guide migration steps.