Create EventController with CRUD Operations

Description

Implement RESTful EventController with all CRUD operations.

Acceptance Criteria

• index() - list events with pagination
• store() - create event with validation
• show() - get single event with attendances
• update() - update event
• destroy() - delete event
• Proper HTTP status codes
• Eager loading to prevent N+1

Implementation Steps

1. php artisan make:controller Api/EventController --api
2. Implement all CRUD methods
3. Use Form Requests for validation
4. Return API Resources
5. Add to routes/api.php

Reference

• Roadmap: docs/roadmaps/Implementation_Roadmap_Backend.md Phase 4, Step 8-9
• Standards: backend/CLAUDE.md - Controllers section

Related Issues

• Depends on: #6, #7
• Blocks: #12