fix: Database-first cluster status detection + Stop button clarification

CRITICAL FIX (Nov 30, 2025):
- Dashboard showed 'idle' despite 22+ worker processes running
- Root cause: SSH-based worker detection timing out
- Solution: Check database for running chunks FIRST

Changes:
1. app/api/cluster/status/route.ts:
   - Query exploration database before SSH detection
   - If running chunks exist, mark workers 'active' even if SSH fails
   - Override worker status: 'offline' → 'active' when chunks running
   - Log: '✅ Cluster status: ACTIVE (database shows running chunks)'
   - Database is source of truth, SSH only for supplementary metrics

2. app/cluster/page.tsx:
   - Stop button ALREADY EXISTS (conditionally shown)
   - Shows Start when status='idle', Stop when status='active'
   - No code changes needed - fixed by status detection

Result:
- Dashboard now shows 'ACTIVE' with 2 workers (correct)
- Workers show 'active' status (was 'offline')
- Stop button automatically visible when cluster active
- System resilient to SSH timeouts/network issues

Verified:
- Container restarted: Nov 30 21:18 UTC
- API tested: Returns status='active', activeWorkers=2
- Logs confirm: Database-first logic working
- Workers confirmed running: 22+ processes on worker1, workers on worker2

backtester/math_utils.py

@@ -39,8 +39,9 @@ def calculate_adx(df: pd.DataFrame, length: int) -> pd.Series:
     tr.iloc[0] = (high.iloc[0] - low.iloc[0])
 
     atr = rma(tr, length)
-    plus_di = 100.0 * rma(pd.Series(plus_dm), length) / atr
-    minus_di = 100.0 * rma(pd.Series(minus_dm), length) / atr
+    # CRITICAL FIX: Preserve index when creating Series to avoid doubling on division
+    plus_di = 100.0 * rma(pd.Series(plus_dm, index=df.index), length) / atr
+    minus_di = 100.0 * rma(pd.Series(minus_dm, index=df.index), length) / atr
     dx = 100.0 * (plus_di - minus_di).abs() / (plus_di + minus_di).replace(0, np.nan)
     dx = dx.fillna(0.0)
     return rma(dx, length)