Fix circular dependency: Remove explicit foreign key references and let Sequelize handle relationships

backend/config/database.js

@@ -19,6 +19,10 @@ const sequelize = new Sequelize(
     define: {
       timestamps: true,
       underscored: false
+    },
+    sync: {
+      force: false,
+      alter: false
     }
   }
 );

backend/models/Assignment.js

@@ -9,19 +9,11 @@ const Assignment = sequelize.define('Assignment', {
   },
   trainerId: {
     type: DataTypes.UUID,
-    allowNull: false,
-    references: {
-      model: 'Users',
-      key: 'id'
-    }
+    allowNull: false
   },
   courseId: {
     type: DataTypes.UUID,
-    allowNull: false,
-    references: {
-      model: 'Courses',
-      key: 'id'
-    }
+    allowNull: false
   },
   title: {
     type: DataTypes.STRING,

backend/models/Attendance.js

@@ -9,19 +9,11 @@ const Attendance = sequelize.define('Attendance', {
   },
   userId: {
     type: DataTypes.UUID,
-    allowNull: false,
-    references: {
-      model: 'Users',
-      key: 'id'
-    }
+    allowNull: false
   },
   courseId: {
     type: DataTypes.UUID,
-    allowNull: false,
-    references: {
-      model: 'Courses',
-      key: 'id'
-    }
+    allowNull: false
   },
   date: {
     type: DataTypes.DATEONLY,

backend/models/Course.js

@@ -9,11 +9,7 @@ const Course = sequelize.define('Course', {
   },
   trainerId: {
     type: DataTypes.UUID,
-    allowNull: false,
-    references: {
-      model: 'Users',
-      key: 'id'
-    }
+    allowNull: false
   },
   title: {
     type: DataTypes.STRING,

backend/models/Enrollment.js

@@ -9,19 +9,11 @@ const Enrollment = sequelize.define('Enrollment', {
   },
   userId: {
     type: DataTypes.UUID,
-    allowNull: false,
-    references: {
-      model: 'Users',
-      key: 'id'
-    }
+    allowNull: false
   },
   courseId: {
     type: DataTypes.UUID,
-    allowNull: false,
-    references: {
-      model: 'Courses',
-      key: 'id'
-    }
+    allowNull: false
   },
   status: {
     type: DataTypes.ENUM('pending', 'active', 'completed', 'cancelled'),

backend/scripts/setup-database.js

@@ -8,7 +8,11 @@ const setupDatabase = async () => {
   try {
     console.log('🔄 Setting up database...');
     
-    // Sync database
+    // Test database connection
+    await sequelize.authenticate();
+    console.log('✅ Database connection established.');
+    
+    // Sync database with force to recreate all tables
     await sequelize.sync({ force: true });
     console.log('✅ Database synchronized successfully.');