Implement vocab course and grammar exercise features in backend and frontend

- Added new course management functionalities in VocabController, including creating, updating, and deleting courses and lessons.
- Implemented enrollment and progress tracking for courses, along with grammar exercise creation and management.
- Updated database schema to include tables for courses, lessons, enrollments, and grammar exercises.
- Enhanced frontend with new routes and views for course listing and details, including internationalization support for course-related texts.
- Improved user experience by adding navigation to courses from the main vocab trainer view.

backend/models/community/vocab_course_progress.js

@@ -0,0 +1,56 @@
+import { Model, DataTypes } from 'sequelize';
+import { sequelize } from '../../utils/sequelize.js';
+
+class VocabCourseProgress extends Model {}
+
+VocabCourseProgress.init({
+    id: {
+        type: DataTypes.INTEGER,
+        primaryKey: true,
+        autoIncrement: true
+    },
+    userId: {
+        type: DataTypes.INTEGER,
+        allowNull: false,
+        field: 'user_id'
+    },
+    courseId: {
+        type: DataTypes.INTEGER,
+        allowNull: false,
+        field: 'course_id'
+    },
+    lessonId: {
+        type: DataTypes.INTEGER,
+        allowNull: false,
+        field: 'lesson_id'
+    },
+    completed: {
+        type: DataTypes.BOOLEAN,
+        allowNull: false,
+        defaultValue: false
+    },
+    score: {
+        type: DataTypes.INTEGER,
+        allowNull: false,
+        defaultValue: 0
+    },
+    lastAccessedAt: {
+        type: DataTypes.DATE,
+        allowNull: true,
+        field: 'last_accessed_at'
+    },
+    completedAt: {
+        type: DataTypes.DATE,
+        allowNull: true,
+        field: 'completed_at'
+    }
+}, {
+    sequelize,
+    modelName: 'VocabCourseProgress',
+    tableName: 'vocab_course_progress',
+    schema: 'community',
+    timestamps: false,
+    underscored: true
+});
+
+export default VocabCourseProgress;