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/snowflake-dbt-dataflow.mmd

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+flowchart TB
+    subgraph Input["Data Ingestion"]
+        SNB["SnowBridge<br/>(Historian SQL + Redpanda)"]
+    end
+
+    subgraph Snowflake["Snowflake + dbt"]
+        direction TB
+        LAND["Landing Tables<br/>(raw, as-received)"]
+        STG["Staging Models<br/>(cleaned, typed)"]
+        subgraph Curated["Curated Layer (canonical model)"]
+            DIM["dim_equipment<br/>(UUID + 5 identifiers<br/>+ UNS path + class)"]
+            STATE["fact_state_transitions<br/>(Running/Idle/Faulted/<br/>Starved/Blocked)"]
+            TAGS["fact_tag_values<br/>(time-series, filtered)"]
+            OEE["mart_oee<br/>(cross-site OEE<br/>from canonical state)"]
+            EVENTS["fact_events<br/>(canonical event stream)"]
+        end
+        TESTS["dbt tests<br/>(enum divergence checks,<br/>source freshness ≤15min)"]
+    end
+
+    subgraph Consumers["Analytics Consumers"]
+        PBI["Power BI<br/>(reporting)"]
+        AIML["AI/ML Models<br/>(predictive)"]
+        ADHOC["Ad-hoc SQL<br/>(analysts)"]
+    end
+
+    SNB --> LAND
+    LAND --> STG
+    STG --> DIM
+    STG --> STATE
+    STG --> TAGS
+    STATE --> OEE
+    TAGS --> OEE
+    DIM --> PBI
+    OEE --> PBI
+    EVENTS --> AIML
+    STATE --> AIML
+    DIM --> ADHOC
+    TAGS --> ADHOC
+    TESTS -.->|"validates"| Curated