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)

backend/src/controllers/template.controller.js

@@ -1,6 +1,11 @@
 const { MailTemplate } = require('../models');
 const mailService = require('../services/mail.service');
 
+const buildTemplateResponse = (template) => ({
+  success: true,
+  data: template,
+});
+
 // Get all templates
 exports.getAllTemplates = async (req, res, next) => {
   try {
@@ -17,6 +22,25 @@ exports.getAllTemplates = async (req, res, next) => {
   }
 };
 
+// Get template by ID
+exports.getTemplateById = async (req, res, next) => {
+  try {
+    const { id } = req.params;
+    const template = await MailTemplate.findByPk(id);
+
+    if (!template) {
+      return res.status(404).json({
+        success: false,
+        error: 'Template not found',
+      });
+    }
+
+    res.json(buildTemplateResponse(template));
+  } catch (error) {
+    next(error);
+  }
+};
+
 // Get template by type
 exports.getTemplateByType = async (req, res, next) => {
   try {
@@ -33,9 +57,71 @@ exports.getTemplateByType = async (req, res, next) => {
       });
     }
 
+    res.json(buildTemplateResponse(template));
+  } catch (error) {
+    next(error);
+  }
+};
+
+// Create template
+exports.createTemplate = async (req, res, next) => {
+  try {
+    const template = await MailTemplate.create(req.body);
+    res.status(201).json(buildTemplateResponse(template));
+  } catch (error) {
+    if (error.name === 'SequelizeUniqueConstraintError') {
+      return res.status(400).json({
+        success: false,
+        error: 'Bu template_type değeri zaten kullanılıyor.',
+      });
+    }
+    next(error);
+  }
+};
+
+// Update template
+exports.updateTemplate = async (req, res, next) => {
+  try {
+    const { id } = req.params;
+
+    const template = await MailTemplate.findByPk(id);
+    if (!template) {
+      return res.status(404).json({
+        success: false,
+        error: 'Template not found',
+      });
+    }
+
+    await template.update(req.body);
+    res.json(buildTemplateResponse(template));
+  } catch (error) {
+    if (error.name === 'SequelizeUniqueConstraintError') {
+      return res.status(400).json({
+        success: false,
+        error: 'Bu template_type değeri zaten kullanılıyor.',
+      });
+    }
+    next(error);
+  }
+};
+
+// Delete template
+exports.deleteTemplate = async (req, res, next) => {
+  try {
+    const { id } = req.params;
+
+    const template = await MailTemplate.findByPk(id);
+    if (!template) {
+      return res.status(404).json({
+        success: false,
+        error: 'Template not found',
+      });
+    }
+
+    await template.destroy();
     res.json({
       success: true,
-      data: template,
+      message: 'Template deleted successfully',
     });
   } catch (error) {
     next(error);
@@ -68,5 +154,4 @@ exports.previewTemplate = async (req, res, next) => {
   }
 };
 
-module.exports = exports;
-
+module.exports = exports;

backend/src/routes/template.routes.js

@@ -2,13 +2,22 @@ const express = require('express');
 const router = express.Router();
 const templateController = require('../controllers/template.controller');
 const { requireAuth } = require('../middlewares/auth');
+const {
+  validateCreateTemplate,
+  validateUpdateTemplate,
+  validatePreviewTemplate,
+} = require('../validators/template.validator');
 
 // All template routes require authentication
 router.use(requireAuth);
 
 router.get('/', templateController.getAllTemplates);
-router.get('/:type', templateController.getTemplateByType);
-router.post('/preview', templateController.previewTemplate);
+router.post('/', validateCreateTemplate, templateController.createTemplate);
+router.get('/:id(\\d+)', templateController.getTemplateById);
+router.put('/:id(\\d+)', validateUpdateTemplate, templateController.updateTemplate);
+router.delete('/:id(\\d+)', templateController.deleteTemplate);
+router.get('/type/:type', templateController.getTemplateByType);
+router.post('/preview', validatePreviewTemplate, templateController.previewTemplate);
 
 module.exports = router;
 

backend/src/validators/template.validator.js

@@ -0,0 +1,63 @@
+const Joi = require('joi');
+
+const baseSchema = {
+  name: Joi.string().max(255).required(),
+  template_type: Joi.string().max(50).required(),
+  subject_template: Joi.string().max(500).allow('', null),
+  body_html: Joi.string().required(),
+  description: Joi.string().allow('', null),
+  active: Joi.boolean().default(true),
+};
+
+const createSchema = Joi.object(baseSchema);
+
+const updateSchema = Joi.object({
+  ...baseSchema,
+});
+
+const previewSchema = Joi.object({
+  template_html: Joi.string().required(),
+  company_name: Joi.string().allow('', null),
+  employee_name: Joi.string().allow('', null),
+});
+
+exports.validateCreateTemplate = (req, res, next) => {
+  const { error, value } = createSchema.validate(req.body, { abortEarly: false });
+  if (error) {
+    return res.status(400).json({
+      success: false,
+      error: 'Validation failed',
+      details: error.details.map((detail) => detail.message),
+    });
+  }
+  req.body = value;
+  next();
+};
+
+exports.validateUpdateTemplate = (req, res, next) => {
+  const { error, value } = updateSchema.validate(req.body, { abortEarly: false });
+  if (error) {
+    return res.status(400).json({
+      success: false,
+      error: 'Validation failed',
+      details: error.details.map((detail) => detail.message),
+    });
+  }
+  req.body = value;
+  next();
+};
+
+exports.validatePreviewTemplate = (req, res, next) => {
+  const { error, value } = previewSchema.validate(req.body, { abortEarly: false });
+  if (error) {
+    return res.status(400).json({
+      success: false,
+      error: 'Validation failed',
+      details: error.details.map((detail) => detail.message),
+    });
+  }
+  req.body = value;
+  next();
+};
+
+