Add integration test suite for API contract validation

[JoshSalway]

Summary

• Adds tests/Integration/ApiContractTest.php with 9 read-only integration tests that hit the real Laravel Cloud API to validate DTO contracts
• Tests cover: applications (list + get), environments, database clusters, caches, buckets, IP addresses, organization metadata, and regions
• All tests use the integration group and skip gracefully when LARAVEL_CLOUD_API_TOKEN is not set
• Integration tests are excluded from the default ./vendor/bin/pest run via <groups><exclude> in phpunit.xml.dist
• No resources are ever created, updated, or deleted — strictly read-only

How to run

# Default test suite (integration tests excluded)
./vendor/bin/pest

# Integration tests only
LARAVEL_CLOUD_API_TOKEN=xxx ./vendor/bin/pest --group=integration

Closes #88

Test plan

• Existing 31 tests still pass with ./vendor/bin/pest
• Integration tests are excluded from default runs
• Integration tests skip gracefully without LARAVEL_CLOUD_API_TOKEN
• Integration tests pass against real API with valid token

🤖 Generated with Claude Code