Add isolated parallel database environments

[AGiorgetti]

What changed

• replaced the legacy platform-specific Docker Compose setup with Linux-container-only base, dynamic, debug, test, and CI Compose files
• added cross-platform start-environment and stop-environment scripts
• derived isolated Compose project names from normalized worktree or explicit environment names
• added dynamic host port allocation for parallel worktrees and fixed debug/test/CI port presets
• preserved data by default and added --remove-data cleanup
• generated ignored .env files containing the resolved connection strings
• updated the shared test connection factory to load the nearest repository .env file while preserving process environment variable precedence
• updated GitHub Actions to start the same database stack through start-environment.sh ci and clean it up through stop-environment.sh ci --remove-data
• updated VS Code tasks and documentation

Fixed ports

Database	Debug	Test	CI
SQL Server	50001	51001	52001
MySQL	50003	51003	52003
PostgreSQL	50004	51004	52004
Oracle	50005	51005	52005

Why

Multiple Git worktrees and autonomous agents need to run complete SQL persistence database stacks in parallel without container, port, network, or volume collisions. Fixed debug and test environments remain available for predictable human workflows, while GitHub Actions uses the reserved CI environment instead of maintaining duplicate service definitions.

Validation

• reviewed the complete branch diff against develop
• verified all Compose services use Linux images and project-scoped resources
• verified the .env loader is shared by all database-specific test projects through NEventStore.Persistence.Sql.Tests
• verified the CI workflow starts and stops the reserved ci environment for every modern TFM job
• full Docker and .NET execution is delegated to GitHub Actions

Review notes

The branch intentionally removes the obsolete Windows-container Compose file and legacy DockerComposeUp.ps1 / DockerComposeDown.ps1 scripts. Generated .env files are local-only and excluded from Git.