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/components/layout/MobileNav.tsx

@@ -6,6 +6,7 @@ const navItems = [
   { to: '/', label: 'Overview', end: true },
   { to: '/market', label: 'Market', end: false },
   { to: '/signals', label: 'Signals', end: false },
+  { to: '/regime', label: 'Regime', end: false },
 ];
 
 export default function MobileNav() {

frontend/src/components/layout/Sidebar.tsx

@@ -8,6 +8,7 @@ const navItems = [
   { to: '/', label: 'Overview', index: '01', end: true },
   { to: '/market', label: 'Market', index: '02', end: false },
   { to: '/signals', label: 'Signals', index: '03', end: false },
+  { to: '/regime', label: 'Regime', index: '04', end: false },
 ];
 
 const linkClasses = (isActive: boolean) =>
@@ -62,7 +63,7 @@ export default function Sidebar() {
         ))}
         {role === 'admin' && (
           <NavLink to="/admin" className={({ isActive }) => linkClasses(isActive)}>
-            <span className="font-mono text-[10px] tracking-widest opacity-50">04</span>
+            <span className="font-mono text-[10px] tracking-widest opacity-50">05</span>
             Admin
           </NavLink>
         )}