feat: UI nav, onboarding, L2CS weights path + torch.load; trim dev files

Sorry the previous commit came from feature/ui-fix not feature/integration-cleaned xD

Start merging everything before 17/03/26

chore: MLP pipeline, evaluation updates, feature importance, confusion matrices

chore: integration cleanup — remove eye CNN, add threshold justification, fix pipeline

Update .gitignore

Put all the models together (expect UI)

reorg folders, add MLP demo

set up template with folder structure and training script