feat: add standalone AI/Tech regime-change monitor tab

A new /regime tab scoring how far the AI/Tech bull regime has deteriorated
toward a re-rating as a single 0-100 index with per-signal breakdown and a
7/30-day trend. Intentionally decoupled: nothing reads its output to gate or
score trades — the daily-pipeline membership is scheduling only.

- regime_monitor_service: price sub-scores (P1-P6 via Alpaca, like
  market_regime), VIX + HY credit spreads via a small FRED helper, weighted
  aggregation over available signals (missing source -> n/a, dropped from the
  denominator), one snapshot row/day, and a ~90-day history backfill by
  replaying the already-fetched series as-of each past day.
- F1/F3 fundamentals proposed by the configured grounded LLM (reuses
  sentiment_provider_service config resolution), with a manual override + lock.
- regime_snapshots table (migration 011); endpoints on the existing market
  router; admin-editable weights/threshold; standalone /regime page.

Data needs: prices via Alpaca, VIX/credit via FRED (optional key — signals show
n/a without it). No LLM needed for history.

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

app/config.py

@@ -37,6 +37,10 @@ class Settings(BaseSettings):
     # Fundamentals Provider — Alpha Vantage (optional fallback)
     alpha_vantage_api_key: str = ""
 
+    # Regime Monitor — FRED (VIX level + HY credit spreads). Optional: without it
+    # the volatility (P5) and credit-spread (F2) signals are reported as n/a.
+    fred_api_key: str = ""
+
     # Alerts — Telegram (optional env fallback; can also be set in Admin)
     telegram_bot_token: str = ""
     telegram_chat_id: str = ""