Add inbound Web API to ScadaBridge diagrams

Dataflow: inbound Web API (API key auth) added as a third input to scripts
Topology: API callers shown with two paths — direct to any site cluster
OR routed through central hub to reach sites

outputs/diagrams/scadabridge-dataflow.mmd

@@ -2,6 +2,7 @@ flowchart LR
     subgraph Inputs["Data Inputs"]
         OT["OtOpcUa<br/>Equipment NS"]
         SP["OtOpcUa<br/>System Platform NS"]
+        API_IN["Inbound Web API<br/>(API key auth)"]
     end
 
     subgraph ScadaBridge["ScadaBridge Cluster (per site)"]
@@ -27,6 +28,7 @@ flowchart LR
 
     OT --> SCR
     SP --> SCR
+    API_IN --> SCR
     TPL --> SCR
     SCR --> SAF
     SAF --> RED