feat(events): add tag selector to admin event form

server/models/event.js

@@ -142,6 +142,7 @@ const eventSchema = new mongoose.Schema({
   maxAttendees: Number,
   registrationRequired: { type: Boolean, default: false },
   registrationDeadline: Date,
+  tags: [String], // Tag slugs from Tag collection
   agenda: [String],
   speakers: [
     {