Files for Todo_admin added

Backend/models/User.js

@@ -0,0 +1,47 @@
+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
+  },
+  role: { 
+    type: String, enum: ['user', 'admin'], default: 'user' }
+}, {
+  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);