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>

frontend/src/App.tsx

@@ -6,6 +6,7 @@ import RegisterPage from './pages/RegisterPage';
 import DashboardPage from './pages/DashboardPage';
 import MarketPage from './pages/MarketPage';
 import SignalsPage from './pages/SignalsPage';
+import RegimePage from './pages/RegimePage';
 import TickerDetailPage from './pages/TickerDetailPage';
 import AdminPage from './pages/AdminPage';
 
@@ -19,6 +20,7 @@ export default function App() {
           <Route path="/" element={<DashboardPage />} />
           <Route path="/market" element={<MarketPage />} />
           <Route path="/signals" element={<SignalsPage />} />
+          <Route path="/regime" element={<RegimePage />} />
           <Route path="/ticker/:symbol" element={<TickerDetailPage />} />
           {/* Legacy routes from the old 6-page layout */}
           <Route path="/watchlist" element={<Navigate to="/market" replace />} />