Add 5 component data-flow diagrams (Mermaid source + PNG)

- otopcua-dataflow: equipment → drivers (8, with stability tiers) → namespaces → ACL → consumers
- redpanda-eventhub: site ScadaBridge → store-and-forward → central cluster (topics + retention tiers + schema registry) → enterprise consumers
- snowbridge-dataflow: source adapters (Historian/Redpanda) → governed selection + approval workflow → Snowflake landing
- scadabridge-dataflow: OtOpcUa inputs → scripts/templates → multiple outputs (Redpanda, Web APIs, DB, email, equipment writes, Camstar)
- snowflake-dbt-dataflow: landing → staging → curated layer (dim_equipment, fact_state_transitions, mart_oee) → Power BI / AI/ML / ad-hoc

outputs/diagrams/otopcua-dataflow.mmd

@@ -0,0 +1,50 @@
+flowchart LR
+    subgraph Equipment["Equipment (Layer 1)"]
+        PLC1["Modbus TCP/RTU<br/>devices"]
+        PLC2["Siemens S7<br/>PLCs"]
+        PLC3["OPC UA-native<br/>equipment"]
+        PLC4["AB CIP/Legacy<br/>PLCs"]
+        PLC5["Beckhoff TwinCAT<br/>controllers"]
+        CNC["FANUC CNC<br/>(FOCAS)"]
+    end
+
+    subgraph OtOpcUa["OtOpcUa Cluster — per site (Layer 2)"]
+        direction TB
+        subgraph Drivers["Core Drivers (8)"]
+            D1["Modbus<br/>Tier A"]
+            D2["S7<br/>Tier B"]
+            D3["OPC UA Client<br/>Tier A"]
+            D4["AB CIP + Legacy<br/>Tier B"]
+            D5["TwinCAT<br/>Tier B"]
+            D6["FOCAS<br/>Tier C ⚡"]
+        end
+        subgraph Namespaces["Two Namespaces"]
+            EN["Equipment NS<br/>(raw data)"]
+            SPN["System Platform NS<br/>(processed data)"]
+        end
+        ACL["ACL Enforcer<br/>6-level scope"]
+    end
+
+    subgraph Consumers["Downstream Consumers"]
+        SB["ScadaBridge<br/>(Tier 1 cutover)"]
+        IG["Ignition SCADA<br/>(Tier 2 cutover)"]
+        SP["System Platform IO<br/>(Tier 3 cutover)"]
+    end
+
+    PLC1 --> D1
+    PLC2 --> D2
+    PLC3 --> D3
+    PLC4 --> D4
+    PLC5 --> D5
+    CNC -.->|"out-of-process<br/>named pipe"| D6
+    D1 --> EN
+    D2 --> EN
+    D3 --> EN
+    D4 --> EN
+    D5 --> EN
+    D6 --> EN
+    EN --> ACL
+    SPN --> ACL
+    ACL --> SB
+    ACL --> IG
+    ACL --> SP