feat: add support for saving values to original model

[leek]

This PR adds support for storing custom field values directly in entity model columns instead of the custom_field_values table. This is particularly useful for system-defined fields that map to existing database columns while maintaining the custom fields UI for managing field metadata.

Features Added

1. Entity Column Storage Flag

• Added uses_entity_column boolean flag to custom_fields table
• When enabled, field values are stored directly in the entity model's column (matching the field code)
• Regular custom fields continue to use the custom_field_values table

2. Option Value/Label Separation

• Added value column to custom_field_options table
• Allows storing distinct values (e.g., 'M') and labels (e.g., 'Male') for select/choice fields
• Backward compatible: falls back to option id when value is null
• Particularly useful for enum-based fields with specific database values

4. UI Enhancements

• Added "Store in Entity Column" toggle in field management form
• Dynamic options table showing either "Value" or "Color" columns based on settings
• System-defined fields can now have their label edited (while keeping code/type locked)

Use Case Example

  // Create a system-defined field that maps to the 'sex' column on Patient model
  $field = $this->migrator->new(
      model: Patient::class,
      fieldData: new CustomFieldData(
          name: 'Sex',
          code: 'sex',
          type: 'select',
          section: $section,
          systemDefined: true,
          usesEntityColumn: true,  // ← Stores in patients.sex column
      )
  );

  $field->options([
      ['value' => 'M', 'label' => 'Male'],
      ['value' => 'F', 'label' => 'Female'],
  ]);

  $field->create();

Breaking Changes

None - this is a fully backward-compatible addition. Existing fields without uses_entity_column set will continue working as before.