[FEATURE]: Add createSchemaFactory to drizzle-valibot

### Feature hasn't been suggested before.

- [x] I have verified this feature I'm about to request hasn't been suggested before.

### Describe the enhancement you want to request

`drizzle-zod` and `drizzle-typebox` both export `createSchemaFactory`, but `drizzle-valibot` does not. This makes it harder to move between the validator packages and leaves no way to configure type coercion for Valibot schemas.

I propose adding the same factory to `drizzle-valibot`:

```ts
import { createSchemaFactory } from 'drizzle-valibot';

const { createSelectSchema, createInsertSchema, createUpdateSchema } = createSchemaFactory({ coerce: true });
```

Valibot has no global coerce option like Zod, but the factory can generate transform pipes for the affected columns instead. I am the author of Valibot and happy to open a PR if you are interested in this.

Start by comparing the existing createSchemaFactory APIs in drizzle-zod and drizzle-typebox with the current drizzle-valibot schema creators. Trace how Valibot schemas handle affected columns and determine how the coerce option should generate transform pipes. Done means drizzle-valibot exports createSchemaFactory with the three requested schema creators and supports the shown coerce configuration consistently.

Written by the indexing model from the issue text.