Added files of the Todo app

Backend/models/Todo.js

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+import mongoose from 'mongoose';
+
+const todoSchema = new mongoose.Schema({
+  title: {
+    type: String,
+    required: true,
+    trim: true,
+    maxlength: 200
+  },
+  description: {
+    type: String,
+    trim: true,
+    maxlength: 1000
+  },
+  completed: {
+    type: Boolean,
+    default: false
+  },
+  priority: {
+    type: String,
+    enum: ['low', 'medium', 'high'],
+    default: 'medium'
+  },
+  dueDate: {
+    type: Date,
+    required: true
+  },
+  userId: {
+    type: mongoose.Schema.Types.ObjectId,
+    ref: 'User',
+    required: true
+  }
+}, {
+  timestamps: true
+});
+
+export default mongoose.model('Todo', todoSchema);

Backend/models/User.js

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+import mongoose from 'mongoose';
+import bcrypt from 'bcryptjs';
+
+const userSchema = new mongoose.Schema({
+  username: {
+    type: String,
+    required: true,
+    unique: true,
+    trim: true,
+    minlength: 3,
+    maxlength: 30
+  },
+  email: {
+    type: String,
+    required: true,
+    unique: true,
+    trim: true,
+    lowercase: true
+  },
+  password: {
+    type: String,
+    required: true,
+    minlength: 6
+  }
+}, {
+  timestamps: true
+});
+
+userSchema.pre('save', async function(next) {
+  if (!this.isModified('password')) return next();
+  
+  try {
+    const salt = await bcrypt.genSalt(10);
+    this.password = await bcrypt.hash(this.password, salt);
+    next();
+  } catch (error) {
+    next(error);
+  }
+});
+
+userSchema.methods.comparePassword = async function(candidatePassword) {
+  return bcrypt.compare(candidatePassword, this.password);
+};
+
+export default mongoose.model('User', userSchema);