feat: add unified server management

[cotore-game]

Summary

• make piped and version-pinned installation reliable, manage the user PATH, and require explicit initial setup
• add persistent English/Japanese language selection and improve the TUI color theme
• add server listing and lifecycle commands for start, stop, restart, status, logs, and down
• replace direct server.properties editing with a unified server.env settings TUI backed by itzg environment variables
• migrate existing generated servers safely after confirmation, with a compose.yaml.mcserver-kit.bak backup

Server settings

The TUI now manages MOTD, difficulty, game mode, player limit, online mode, whitelist and OP synchronization, flight, command blocks, PvP, distances, spawn settings, resource packs, and other supported values from one source of truth.

After saving, Docker Compose is validated and the user can choose whether to recreate the services immediately.

Compatibility and safety

• existing global config, language, MCID templates, and created servers are preserved by installer updates
• existing server migration is opt-in and leaves the server unchanged when cancelled
• the original Compose file is backed up before migration
• server.env, .env, and private configuration files use mode 600
• path traversal through server IDs is rejected

Verification

• 92 specification tests passed locally; one nested-ZIP test was skipped because the host lacks zip
• both locale catalogs validated
• Bash and Python syntax checks passed
• Docker-based ShellCheck passed
• a copied intervention server configuration migrated successfully and passed docker compose config --quiet; the real server was not modified

Notes

• the pre-existing local CRLF-only LICENSE difference is not included
• this PR intentionally targets main as the next release candidate