docs: convert all ASCII charts to Mermaid diagrams

Converted 40+ ASCII art diagrams across 12 files to Mermaid:
- flowchart TD/LR for process flows and architecture
- erDiagram for entity relationships
- graph TD for tree structures (binary tree, categories)
- gantt for roadmap sprints

Files: BUSINESS-01 to 05, TECH-01/03/04/05, OVERVIEW-01/02/05
Directory tree structures kept as plain code blocks (Mermaid N/A)

technical/TECH-05-API-INTEGRATION.md

@@ -294,21 +294,12 @@ public class ProductService : IProductService
 
 ## ۵. Proto Package Distribution
 
-```
-CMS/src/Protos/*.proto
-    │
-    ▼
-pack-protos.sh
-    │
-    ▼
-Foursat.CMSMicroservice.Protobuf.nupkg (v1.0.x)
-    │
-    ▼
-Push to BaGet (http://localhost:5555) or Nexus
-    │
-    ▼
-BackOffice: <PackageReference Include="Foursat.CMSMicroservice.Protobuf" />
-FrontOffice: <PackageReference Include="Foursat.CMSMicroservice.Protobuf" />
+```mermaid
+flowchart TD
+    A["CMS/src/Protos/*.proto"] --> B["pack-protos.sh"]
+    B --> C["Foursat.CMSMicroservice.Protobuf.nupkg\nv1.0.x"]
+    C --> D["Push to BaGet / Nexus"]
+    D --> E["BackOffice + FrontOffice\nPackageReference"]
 ```
 
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