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-04-MIGRATION.md

@@ -23,30 +23,24 @@ Timeline:
 
 ### ۲.۱ قبل
 
+```mermaid
+flowchart LR
+    FO1["FrontOffice"] -->|HTTP/REST| BFF["BFF"]
+    BO1["BackOffice"] -->|HTTP/REST| BFF
+    BFF -->|gRPC| CMS1["CMS"]
 ```
-FrontOffice ──HTTP/REST──→ BFF ──gRPC──→ CMS
-BackOffice  ──HTTP/REST──→ BFF ──gRPC──→ CMS
 
-BFF مسئولیت‌ها:
-    • تبدیل REST↔gRPC
-    • Aggregation
-    • Auth proxy
-    • Rate limiting
-```
+**BFF مسئولیت‌ها:** تبدیل REST↔gRPC • Aggregation • Auth proxy • Rate limiting
 
 ### ۲.۲ بعد (فعلی)
 
+```mermaid
+flowchart LR
+    FO2["FrontOffice"] -->|gRPC| CMS2["CMS مستقیم"]
+    BO2["BackOffice"] -->|gRPC| CMS2
 ```
-FrontOffice ──gRPC──→ CMS (مستقیم)
-BackOffice  ──gRPC──→ CMS (مستقیم)
 
-مزایا:
-    ✅ حذف ۱ سرویس از deployment
-    ✅ کاهش ~50ms latency per request
-    ✅ Type-safety از proto تا UI
-    ✅ ساده‌سازی debug و logging
-    ✅ کاهش maintenance cost
-```
+**مزایا:** ✅ حذف ۱ سرویس • کاهش ~50ms latency • Type-safety از proto تا UI • ساده‌سازی debug
 
 ### ۲.۳ مراحل مهاجرت
 
@@ -78,18 +72,22 @@ BackOffice  ──gRPC──→ CMS (مستقیم)
 
 ### ۳.۱ قبل
 
-```
-Client → nginx → Ocelot Gateway → { CMS, BFF, FileService }
-         ↑
-    URL routing, rate limiting, auth
+```mermaid
+flowchart LR
+    CL1["Client"] --> NG1["nginx"] --> OC["Ocelot Gateway"]
+    OC --> CMS3["CMS"]
+    OC --> BFF2["BFF"]
+    OC --> FS1["FileService"]
 ```
 
 ### ۳.۲ بعد
 
-```
-Client → nginx → Ingress → { CMS, BackOffice, FrontOffice }
-         ↑
-    Path-based routing in Ingress
+```mermaid
+flowchart LR
+    CL2["Client"] --> NG2["nginx"] --> ING["K8s Ingress"]
+    ING --> CMS4["CMS"]
+    ING --> BO3["BackOffice"]
+    ING --> FO3["FrontOffice"]
 ```
 
 ### ۳.۳ دلایل حذف