[Feature Request] Implement LECO to train LoRA for erasing concepts from diffusion models

See https://github.com/p1atdev/LECO, based off https://github.com/rohitgandikota/erasing/tree/main.

This serves to train "sliders"-like LoRA, and I think it would be great addition to the sd-scripts repo.

Read the LECO repository and the referenced erasing implementation to understand the proposed training approach and its integration requirements. Then inspect sd-scripts to identify an appropriate entry point for adding LECO-based LoRA training. Done means the feature is integrated into sd-scripts with a defined training workflow and validation against the referenced behavior.

Written by the indexing model from the issue text.