feat(ql): add DELETE, UPDATE, SELECT statements and field validation

[abalam666]

Summary

• DELETE / UPDATE / SELECT statements: WebdaQL now supports DELETE WHERE ..., UPDATE SET ... WHERE ..., and SELECT field1, field2 WHERE ... (with implicit detection — no SELECT keyword required for comma-separated field lists)
• Case-insensitive statement keywords: DELETE, UPDATE, SET, SELECT, WHERE, TRUE, FALSE can be written in any case (delete where ..., Update Set ..., etc.)
• Runtime field validation: parse(query, allowedFields?) validates SELECT fields and UPDATE SET targets against an allowed field list. Also available standalone via validateQueryFields(query, allowedFields)
• Repository integration: AbstractRepository.getAllowedFields() derives allowed fields from model JSON Schema metadata; MemoryRepository.query() and .iterate() pass them through automatically

Changed files

Package	File	Change
@webda/ql	src/query.ts	Pre-parser for statement prefixes, assignment parsing, implicit SELECT detection, field validation
@webda/ql	src/query.spec.ts	5 new test methods (delete, update, select, allowedFields, caseInsensitiveKeywords)
@webda/ql	README.md	Full rewrite with new syntax documentation
@webda/models	repositories/abstract.ts	getAllowedFields() method
@webda/models	repositories/memory.ts	Pass allowed fields to WebdaQL.parse()
@webda/test	package.json	Fix workspace dependency resolution

Design decision

Statement-level syntax (DELETE/UPDATE/SELECT/WHERE) is handled by a TypeScript pre-parser rather than extending the ANTLR grammar. This avoids making these words reserved tokens (which would break queries using them as field names) and keeps generated files unchanged.

Test plan

• All 19 tests pass (pnpm run test in packages/ql)
• Verify field validation works end-to-end with a real model/repository
• Test with downstream consumers (e.g. @webda/core stores)