- Add build_dataset_from_db() that exports candles from DB, runs feature
engineering, and ingests span annotations into labeled CSV
- Call it automatically in _run_training_background before training starts
- Add POST /training/build-dataset endpoint for standalone use
- Add Next.js proxy route /api/training/build-dataset
- Update TrainingPanel: remove dataset-missing block on Start Training,
show informational message that dataset builds automatically
- TalibPatternPanel: pattern checkboxes, detect button, results summary, clear-all and per-pattern delete
- TrainingPanel: model type selector, dataset info, start training, polling, run history
- ModelSelector: dropdown of completed runs, wired into PredictionPanel for model switching
- page.tsx: integrate all three panels into sidebar, wire callbacks (model load, annotations refresh)
- tasks.md: mark all 39 tasks complete
