fix: generate one() instead of many() for one-to-one relations with unique FK

[Jah-yee]

When a foreign key column has a UNIQUE constraint, the reverse relation should be one() instead of many(), representing a one-to-one relationship.

This fixes the issue where drizzle-kit pull generated many() for the reverse side of one-to-one relationships when the FK column has a UNIQUE constraint.

Before:

export const usersRelations = relations(users, ({ many }) => ({
  profiles: many(profiles), // incorrect - should be one()
}));

After:

export const usersRelations = relations(users, ({ one }) => ({
  profile: one(profiles), // correct for one-to-one
}));

Fixes #5478