feat(signal_v2-phase3b): foundation — config + state + requirements

- config.py: CHRONOS_MODEL env (default amazon/chronos-2)
- state.py: PollState extended with daily_ohlcv + chronos_predictions
  + minute_momentum
- requirements.txt: transformers + chronos-forecasting

33 existing tests still pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

signal_v2/config.py

@@ -34,6 +34,7 @@ class Settings:
                       str(Path(__file__).parent.parent / "signal_v1" / "data" / "kis_token.json"))
         )
     )
+    chronos_model: str = field(default_factory=lambda: os.getenv("CHRONOS_MODEL", "amazon/chronos-2"))
 
     @property
     def kis_is_virtual(self) -> bool: