[Copilot]

Schema::addForeignKey() created a primary-key constraint instead of a foreign-key constraint, so downstream schema handling misidentified it.

• Schema: Use Constraint::TYPE_FOREIGN_KEY when creating the constraint.
• Regression test: Verify the constraint is foreign and not primary.

$constraint = $schema->addForeignKey('category_id', 'categories', 'id');

$constraint->isForeignKey(); // true

• Fixes [DB] Schema::addForeignKey() #1396