Better syntax support in editor

### Description

> ### Additional / alternative.
> - The built in Monaco SQL lang is generic (not PostGresQL aware) and has no completion or checking (it is essentially just syntax highliting). Using a combination of [libpg-query](https://www.npmjs.com/package/libpg-query?activeTab=readme) and (monaco-sql-languages)[https://www.npmjs.com/package/monaco-sql-languages] we could provide a richer experience for `tables` users
> - The addition of `libpg-query` would give us the ability to actually inform the user of syntax errors (like in the function node or JSON editors)

Originally raised in https://github.com/FlowFuse/nr-assistant/issues/66#issuecomment-3200076483

### Epic/Story

_No response_

Start by locating the tables editor's built-in Monaco SQL language integration; the issue does not name repository files or tests. Review libpg-query and monaco-sql-languages to determine how PostgreSQL-aware completion, checking, and syntax-error reporting would fit. Done means the editor provides richer PostgreSQL support, including syntax errors and completion for tables.

Written by the indexing model from the issue text.