Align compose structure and operational workflow

[lraigosov]

Summary

• reorganize service definitions into dedicated compose files
• normalize environment files under env for each stack
• add portainer compose definitions including remote agent option
• harden persistence strategy with project-scoped external volumes
• improve backup and restore guidance for portainer data
• refine runtime validation and operational documentation

Validation performed

• validated compose rendering for all service files using docker compose config
• validated stack behavior with granular start, health verification, and stop cycles
• confirmed only required baseline services remain active after checks

Notes for reviewers

• this PR keeps existing data paths and focuses on safe redeploy behavior
• no branch deletion is required after merge