[core-be-agent] fix(delegations): add rows.Err() check after ledger and activity_logs iteration

rows.Err() must be checked after exhausting rows.Next() to catch any
iteration error (e.g., scan errors, connection issues mid-read). Without
this check, a partial corrupted result could silently be returned.

Fixes gap flagged in PR #250 review.

workspace-server/internal/handlers/delegation.go

@@ -677,6 +677,13 @@ func (h *DelegationHandler) listDelegationsFromLedger(ctx context.Context, works
 		result = append(result, entry)
 	}
 
+	// rows.Err() reports any error encountered during iteration. Must be
+	// checked after exhausting rows.Next() and before using result.
+	if err := rows.Err(); err != nil {
+		log.Printf("listDelegationsFromLedger: rows error: %v", err)
+		return nil
+	}
+
 	if result == nil {
 		return nil
 	}
@@ -732,6 +739,12 @@ func (h *DelegationHandler) listDelegationsFromActivityLogs(ctx context.Context,
 		result = append(result, entry)
 	}
 
+	// rows.Err() reports any error encountered during iteration.
+	if err := rows.Err(); err != nil {
+		log.Printf("listDelegationsFromActivityLogs: rows error: %v", err)
+		return []map[string]interface{}{}
+	}
+
 	if result == nil {
 		return []map[string]interface{}{}
 	}