fix(external-system-gateway): resolve ExternalSystemGateway-011 — name-keyed repository lookups replace fetch-all-then-filter on the call hot path

src/ScadaLink.ExternalSystemGateway/DatabaseGateway.cs

@@ -170,8 +170,10 @@ public class DatabaseGateway : IDatabaseGateway
         string connectionName,
         CancellationToken cancellationToken)
     {
-        var connections = await _repository.GetAllDatabaseConnectionsAsync(cancellationToken);
-        return connections.FirstOrDefault(c =>
-            c.Name.Equals(connectionName, StringComparison.OrdinalIgnoreCase));
+        // ExternalSystemGateway-011: name-keyed repository lookup instead of
+        // fetch-all-then-filter — connection definitions are resolved on every
+        // cached write / connection request, so the repository performs an indexed
+        // query rather than loading every connection into memory.
+        return await _repository.GetDatabaseConnectionByNameAsync(connectionName, cancellationToken);
     }
 }

src/ScadaLink.ExternalSystemGateway/ExternalSystemClient.cs

@@ -373,13 +373,15 @@ public class ExternalSystemClient : IExternalSystemClient
         string methodName,
         CancellationToken cancellationToken)
     {
-        var systems = await _repository.GetAllExternalSystemsAsync(cancellationToken);
-        var system = systems.FirstOrDefault(s => s.Name.Equals(systemName, StringComparison.OrdinalIgnoreCase));
+        // ExternalSystemGateway-011: name-keyed repository lookups instead of
+        // fetch-all-then-filter — definitions are resolved on every hot-path call
+        // (a script's ExternalSystem.Call()), so the repository performs an indexed
+        // query rather than loading every system / every method into memory.
+        var system = await _repository.GetExternalSystemByNameAsync(systemName, cancellationToken);
         if (system == null)
             return (null, null);
 
-        var methods = await _repository.GetMethodsByExternalSystemIdAsync(system.Id, cancellationToken);
-        var method = methods.FirstOrDefault(m => m.Name.Equals(methodName, StringComparison.OrdinalIgnoreCase));
+        var method = await _repository.GetMethodByNameAsync(system.Id, methodName, cancellationToken);
 
         return (system, method);
     }