Add Context APIs and refactor vocab models

Introduce Context and ContextGuide features: add Sequelize models (models/Context.js, models/ContextGuide.js), controllers (controllers/contextController.js, controllers/contextGuideController.js) and authenticated route handlers (routes/contextRoutes.js, routes/contextGuideRoutes.js). Wire the new routes into app.js and export the models from models/index.js. Refactor vocabulary: remove VocabForm, VocabMapping and VocabRelation models and relationships, update models/Vocab.js schema and indexes, and add migrate-vocab.js to drop/recreate the vocab table for the new schema. Also add a lesson editor UI (public/lesson-editor.html) and a small cleanup in models/Lesson.js.

controllers/contextGuideController.js

@@ -0,0 +1,139 @@
+const { ContextGuide } = require('../models');
+
+/**
+ * ContextGuide Controller
+ */
+class ContextGuideController {
+  /**
+   * Get all context guides with pagination and filters
+   */
+  async getAllContextGuides(req, res, next) {
+    try {
+      const { page = 1, limit = 50, name, title } = req.query;
+      const offset = (page - 1) * limit;
+
+      const where = {};
+      if (name) where.name = name;
+      if (title) where.title = title;
+
+      const { count, rows } = await ContextGuide.findAndCountAll({
+        where,
+        limit: parseInt(limit),
+        offset: parseInt(offset),
+        order: [['created_at', 'DESC']]
+      });
+
+      res.json({
+        success: true,
+        data: {
+          guides: rows,
+          pagination: {
+            total: count,
+            page: parseInt(page),
+            limit: parseInt(limit),
+            totalPages: Math.ceil(count / limit)
+          }
+        }
+      });
+    } catch (error) {
+      next(error);
+    }
+  }
+
+  /**
+   * Get context guide by UUID
+   */
+  async getContextGuideById(req, res, next) {
+    try {
+      const { id } = req.params;
+      const guide = await ContextGuide.findByPk(id);
+
+      if (!guide) {
+        return res.status(404).json({
+          success: false,
+          message: 'Context guide not found'
+        });
+      }
+
+      res.json({
+        success: true,
+        data: guide
+      });
+    } catch (error) {
+      next(error);
+    }
+  }
+
+  /**
+   * Create new context guide
+   */
+  async createContextGuide(req, res, next) {
+    try {
+      const guide = await ContextGuide.create(req.body);
+
+      res.status(201).json({
+        success: true,
+        message: 'Context guide created successfully',
+        data: guide
+      });
+    } catch (error) {
+      next(error);
+    }
+  }
+
+  /**
+   * Update context guide
+   */
+  async updateContextGuide(req, res, next) {
+    try {
+      const { id } = req.params;
+      const updates = req.body;
+
+      const guide = await ContextGuide.findByPk(id);
+      if (!guide) {
+        return res.status(404).json({
+          success: false,
+          message: 'Context guide not found'
+        });
+      }
+
+      await guide.update(updates);
+
+      res.json({
+        success: true,
+        message: 'Context guide updated successfully',
+        data: guide
+      });
+    } catch (error) {
+      next(error);
+    }
+  }
+
+  /**
+   * Delete context guide
+   */
+  async deleteContextGuide(req, res, next) {
+    try {
+      const { id } = req.params;
+      const guide = await ContextGuide.findByPk(id);
+
+      if (!guide) {
+        return res.status(404).json({
+          success: false,
+          message: 'Context guide not found'
+        });
+      }
+
+      await guide.destroy();
+
+      res.json({
+        success: true,
+        message: 'Context guide deleted successfully'
+      });
+    } catch (error) {
+      next(error);
+    }
+  }
+}
+
+module.exports = new ContextGuideController();