Add Phase 2 foundation: regime classifier, strategy framework, WebSocket streamer

Phase 1 completion:
- Add DataStreamer for real-time Binance Futures WebSocket data (klines, mark price)
- Add DataValidator for candle validation and gap detection
- Add timeframes module with interval mappings

Phase 2 foundation:
- Add RegimeClassifier with ADX/ATR/Bollinger Band analysis
- Add Regime enum (TRENDING_UP/DOWN, RANGING, HIGH_VOLATILITY, UNCERTAIN)
- Add Strategy ABC defining generate_signal, get_stop_loss, parameters, suitable_regimes
- Add Signal dataclass and SignalType enum for strategy outputs

Testing:
- Add comprehensive test suites for all new modules
- 159 tests passing, 24 skipped (async WebSocket timing)
- 82% code coverage

Dependencies:
- Add pandas-stubs to dev dependencies for mypy compatibility

pyproject.toml

@@ -70,6 +70,7 @@ dev = [
     "ruff>=0.1.0",
     "mypy>=1.8.0",
     "pre-commit>=3.6.0",
+    "pandas-stubs>=2.1.0",
 ]
 email = [
     "jinja2>=3.1.0",