docs: add OMS positioning strategy and implementation plan

- Add "Lightweight OMS for Letzshop Sellers" positioning strategy
- Add back-office vs marketing positioning comparison
- Update pricing tiers for OMS model (Essential/Professional/Business)
- Add VAT invoice feature technical specification
- Add comprehensive OMS feature implementation plan
- Fix code block formatting in synology doc

New docs:
- docs/marketing/strategy/back-office-positioning.md
- docs/marketing/strategy/customer-marketing-positioning.md
- docs/implementation/vat-invoice-feature.md
- docs/implementation/oms-feature-plan.md

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/development/synology-github-repo.md

@@ -55,13 +55,15 @@ Git is an open-source, distributed version control system that helps you manage
    ```
 Adding new repository on NAS DS223J
 
-> ssh boulaht1@DS223J
-> sudo -i
-> cd /volume1/git-repos/
-> git --bare init my-repo.git
-> chown -R git-boulaht1:users my-repo.git
-> cd my-repo.git/
-
+   ```bash
+    > ssh boulaht1@DS223J
+    > sudo -i
+    > cd /volume1/git-repos/
+    > git --bare init my-repo.git
+    > chown -R git-boulaht1:users my-repo.git
+    > cd my-repo.git/
+  ```
+  
 ---
 
 ### ✅ **Steps to Push Local Git Repo to Synology NAS**