docs: render architecture & flow diagrams as draw.io charts

Replace ASCII-art diagrams across the README and docs/ with editable
.drawio sources plus exported PNGs, so the diagrams render clearly in
rendered markdown and can be maintained/regenerated instead of being
hand-edited as fragile text art. Non-diagram blocks (code, folder
trees, UI wireframes) were left as text.

docs/requirements/Component-ConfigurationDatabase.md

@@ -143,15 +143,8 @@ EF Core's DbContext naturally provides unit-of-work semantics:
 
 ### Example Transactional Flow
 
-```
-Template Engine: Create Template
-    │
-    ├── repository.AddTemplate(template)      // template is a Commons POCO
-    ├── repository.AddAttributes(attributes)  // attributes are Commons POCOs
-    ├── repository.AddAlarms(alarms)          // alarms are Commons POCOs
-    ├── repository.AddScripts(scripts)        // scripts are Commons POCOs
-    └── repository.SaveChangesAsync()         // single transaction commits all
-```
+![configdb-transactional-flow](diagrams/configdb-transactional-flow.png)
+<!-- source: diagrams/configdb-transactional-flow.drawio — edit, then re-export with export-drawio.sh -->
 
 ---
 
@@ -184,14 +177,8 @@ Audit entries are written **synchronously** within the same database transaction
 
 ### Integration Example
 
-```
-Template Engine: Update Template
-    │
-    ├── repository.UpdateTemplate(template)
-    ├── auditService.LogAsync(user, "Update", "Template", template.Id,
-    │       template.Name, template)
-    └── repository.SaveChangesAsync()  ← both the change and audit entry commit together
-```
+![configdb-integration-example](diagrams/configdb-integration-example.png)
+<!-- source: diagrams/configdb-integration-example.drawio — edit, then re-export with export-drawio.sh -->
 
 ### Audit Entry Schema