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

scripts/run_backtest_sweep.py

@@ -219,9 +219,20 @@ class ProgressBar:
         elapsed = time.time() - self.start_time
         rate = elapsed / count if count else 0
         remaining = rate * (self.total - count) if rate else 0
+        
+        # Format elapsed time
+        elapsed_hours = int(elapsed // 3600)
+        elapsed_mins = int((elapsed % 3600) // 60)
+        elapsed_str = f"{elapsed_hours}h {elapsed_mins}m" if elapsed_hours > 0 else f"{elapsed_mins}m"
+        
+        # Format remaining time
+        remaining_hours = int(remaining // 3600)
+        remaining_mins = int((remaining % 3600) // 60)
+        remaining_str = f"{remaining_hours}h {remaining_mins}m" if remaining_hours > 0 else f"{remaining_mins}m"
+        
         sys.stdout.write(
             f"\r[{bar}] {percent*100:5.1f}% ({count}/{self.total}) | "
-            f"Elapsed {elapsed:6.1f}s | ETA {remaining:6.1f}s"
+            f"Elapsed {elapsed_str:>7} | ETA {remaining_str:>7}"
         )
         sys.stdout.flush()
         if count >= self.total: