fix: migrate deprecated docker-compose v1 commands to docker compose v2

[rickstaa]

Problem

docker-compose (v1, standalone Python binary) was deprecated in July 2023 and is not installed by default on modern Docker Desktop or Docker Engine setups. Several scripts and docs in the repo still reference the v1 binary directly, causing command not found errors for new developers.

Affected:

• bin/db-setup.sh
• bin/setup-db-simple.sh
• packages/plugin-sdk/cli/commands/dev.ts
• Multiple docs (database.md, TROUBLESHOOTING.md, database-setup.mdx, database-plugin.mdx)

Note: bin/start.sh and bin/stop.sh already handle this correctly with a v2-first fallback helper.

Expected behavior

All scripts should use docker compose (v2 plugin) with a fallback to docker-compose (v1) for backwards compatibility. All docs should reference the v2 syntax.

[github-actions]

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