Simplify UI integration

feat: sync integration updates across app and ML pipeline

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

MERGE EVERYTHING from feature/integration-cleaned :((((((((((((((((((((((((((((((((((((((((((((((( so tired

evaluation: channel ablation script + feature importance LOPO

Merge UI Manually (expect main)

Put all the models together (expect UI)