feat(db): Add unique index for registration number in users collection and remove redundant index for category name

Author: codevoid048

server/lib/dbIndexes.js

@@ -36,7 +36,6 @@ export const createOptimalIndexes = async () => {
         await usersCollection.createIndex({ email: 1 }, { unique: true, sparse: true, name: 'email_unique_idx' });
         await usersCollection.createIndex({ username: 1 }, { unique: true, sparse: true, name: 'username_unique_idx' });
         await usersCollection.createIndex({ registrationNumber: 1 }, { unique: true, sparse: true, name: 'regno_unique_idx' });
-        // Skip RegistrationNumber for now - has duplicates
 
         // Performance indexes for leaderboard
         await usersCollection.createIndex({ points: -1, rank: 1 }, { name: 'leaderboard_sort_idx' });

server/models/Category.js

@@ -11,7 +11,4 @@ const categorySchema = new mongoose.Schema({
     timestamps: true
 });
 
-// Index for fast lookups
-categorySchema.index({ name: 1 });
-
 export const Category = mongoose.model('Category', categorySchema);