test: add integration tests for event workflows

[anxkhn]

Problem Description

The application lacks integration tests that verify complete user workflows.

Context

Integration tests ensure all parts work together correctly, catching issues unit tests miss.

Files to Investigate

• Create src/test/integration/ - New integration test directory
• vitest.config.ts - Test configuration

Expected Behavior

Integration tests should cover key user workflows.

Acceptance Criteria

• Test: Create event -> View event -> Upvote
• Test: Filter events by category
• Test: Search events
• Test: Register for event
• Tests run in CI

Suggested Approach

Use Vitest with testing-library to test user workflows end-to-end.

Difficulty: Hard

Estimated time: 3-6 hours
Prerequisites: Integration testing, testing-library
Learning outcomes: Integration testing, workflow testing