add market-regime guard (SPY trend) — inform + warn

New market_regime_service computes a benchmark (SPY) trend from its 50/200-day
SMAs, cached in a SystemSetting and refreshed by a nightly job; GET /market/regime
exposes it. Dashboard shows a regime banner; setup cards flag a counter-trend
caution when a setup fights the regime (LONG in a bearish market / SHORT in a
bullish one). Informational only — nothing is suppressed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/services/market_regime_service.py

@@ -0,0 +1,115 @@
+"""Market-regime guard.
+
+Computes a simple, robust trend regime for a benchmark (SPY by default) from its
+own moving averages, so the UI can warn against fighting the broad market — e.g.
+going long while SPY is below its 200-day average. Result is cached in a
+SystemSetting (JSON) and refreshed by a daily job; reads are cheap.
+
+Regime is informational: it warns, it doesn't suppress setups.
+"""
+
+from __future__ import annotations
+
+import json
+import logging
+from datetime import date, datetime, timedelta, timezone
+
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.config import settings
+from app.providers.alpaca import AlpacaOHLCVProvider
+from app.services.admin_service import update_setting
+from app.models.settings import SystemSetting
+from sqlalchemy import select
+
+logger = logging.getLogger(__name__)
+
+KEY_REGIME = "market_regime"
+BENCHMARK = "SPY"
+_SMA_SHORT = 50
+_SMA_LONG = 200
+
+
+def _sma(values: list[float], window: int) -> float | None:
+    if len(values) < window:
+        return None
+    return sum(values[-window:]) / window
+
+
+def compute_regime(closes: list[float]) -> dict:
+    """Derive a regime label from a benchmark's close series.
+
+    bullish  = price above the 200-day and the 50-day confirms (50 ≥ 200)
+    bearish  = price below the 200-day and the 50-day confirms (50 ≤ 200)
+    neutral  = mixed / chop
+    unknown  = not enough history
+    """
+    if not closes:
+        return {"label": "unknown", "reason": "no benchmark data"}
+
+    price = closes[-1]
+    sma50 = _sma(closes, _SMA_SHORT)
+    sma200 = _sma(closes, _SMA_LONG)
+
+    if sma200 is None:
+        # Fall back to the 50-day alone when we lack a full year of history.
+        if sma50 is None:
+            return {"label": "unknown", "reason": "insufficient history"}
+        label = "bullish" if price > sma50 else "bearish"
+        return {
+            "label": label,
+            "price": round(price, 2),
+            "sma50": round(sma50, 2),
+            "sma200": None,
+            "pct_above_200": None,
+            "reason": "based on 50-day only (under 200 bars)",
+        }
+
+    above_200 = price > sma200
+    if above_200 and sma50 >= sma200:
+        label = "bullish"
+    elif not above_200 and sma50 <= sma200:
+        label = "bearish"
+    else:
+        label = "neutral"
+
+    return {
+        "label": label,
+        "price": round(price, 2),
+        "sma50": round(sma50, 2),
+        "sma200": round(sma200, 2),
+        "pct_above_200": round((price / sma200 - 1.0) * 100, 2),
+        "reason": None,
+    }
+
+
+async def update_market_regime(db: AsyncSession) -> dict:
+    """Fetch the benchmark, compute the regime, and cache it. Job entrypoint."""
+    if not settings.alpaca_api_key or not settings.alpaca_api_secret:
+        return {"label": "unknown", "reason": "Alpaca keys not configured"}
+
+    provider = AlpacaOHLCVProvider(settings.alpaca_api_key, settings.alpaca_api_secret)
+    end = date.today()
+    start = end - timedelta(days=400)  # ~280 trading days → covers the 200-day SMA
+    bars = await provider.fetch_ohlcv(BENCHMARK, start, end)
+    closes = [b.close for b in sorted(bars, key=lambda b: b.date)]
+
+    regime = compute_regime(closes)
+    regime["benchmark"] = BENCHMARK
+    regime["computed_at"] = datetime.now(timezone.utc).isoformat()
+
+    await update_setting(db, KEY_REGIME, json.dumps(regime))
+    logger.info(json.dumps({"event": "market_regime_updated", "regime": regime["label"]}))
+    return regime
+
+
+async def get_market_regime(db: AsyncSession) -> dict:
+    """Return the cached regime (computed by the daily job)."""
+    result = await db.execute(select(SystemSetting).where(SystemSetting.key == KEY_REGIME))
+    setting = result.scalar_one_or_none()
+    if setting is None:
+        return {"label": "unknown", "benchmark": BENCHMARK, "reason": "not computed yet"}
+    try:
+        return json.loads(setting.value)
+    except (TypeError, ValueError):
+        return {"label": "unknown", "benchmark": BENCHMARK, "reason": "corrupt cache"}