feat: Mail template management UI and API CRUD

- Added full CRUD endpoints for mail templates (create, update, delete, preview)
- Introduced Joi validators for template create/update/preview
- Updated routes/controller to support ID and type lookups
- Built React Templates page with HTML editor, preview, and clipboard helpers
- Added navigation entry and route for /templates
- Enhanced documentation (README, QUICKSTART, KULLANIM, frontend/backend README)

README.md

@@ -10,6 +10,7 @@ Güvenlik farkındalık eğitimleri için basit ve etkili phishing test yönetim
 - 📊 **Detaylı İstatistikler** - IP, konum, cihaz bilgileri
 - 💾 **SQLite** - Tek dosya, kolay yedekleme
 - 🎨 **Modern UI** - React ile responsive admin paneli
+- ✉️ **Mail Şablonları** - HTML editör ve önizleme paneli
 
 ## 🚀 Hızlı Başlangıç
 
@@ -54,7 +55,7 @@ oltalama/
 │   ├── src/
 │   │   ├── services/     ✅ 5 servis (auth, company, token, stats, template)
 │   │   ├── context/      ✅ Auth context
-│   │   ├── pages/        ✅ 5 sayfa (Login, Dashboard, Companies, Tokens, Settings)
+│   │   ├── pages/        ✅ 6 sayfa (Login, Dashboard, Companies, Tokens, Templates, Settings)
 │   │   └── components/   ✅ Layout + Navigation
 └── devpan.md             ✅ Detaylı plan
 ```
@@ -163,8 +164,9 @@ curl http://localhost:3000/api/stats/dashboard
 **Core Pages:**
 - ✅ Login (Session-based auth)
 - ✅ Dashboard (Stats, recent clicks)
-- ✅ Companies (CRUD, grid view)
-- ✅ Tokens (Create & send, table view)
+- ✅ Companies (CRUD, grid view + detail)
+- ✅ Tokens (Create & send, detail & history)
+- ✅ Mail Şablonları (HTML editör + önizleme)
 - ✅ Settings (Gmail, Telegram config)
 
 **Components:**