Add useFineTuneStore (Pinia setup-function) with step state, polling via
setInterval, loadStatus, startPolling/stopPolling, and submitJob. Add
FineTuneView.vue with a 3-step wizard (upload → extract → train), mode-aware
train step (self-hosted shows make finetune + model check; cloud shows
submit job + quota). Add fine-tune endpoints to dev-api.py: status, extract,
upload, submit, and local-status. All 4 store unit tests pass.
