Add DatabaseTestBase.cs with xUnit Collection for test isolation:
- DatabaseTestCollection disables parallel execution
- DatabaseTestFixture verifies database connectivity
- DatabaseTestBase provides connection and cleanup helpers
- InsertTestSearchAsync for creating test data with SearchCriteria
- InsertTestSearchWithRawCriteriaAsync for testing invalid JSON scenarios
Also adds required packages: Dapper, FluentAssertions, Microsoft.Data.SqlClient
Joseph Doherty