Add troubleshooting guide

[kiyeonjeon21]

Priority: P1

No troubleshooting documentation exists.

What to do

Create docs/troubleshooting.md covering:

• Port conflicts, insufficient memory, healthcheck failures
• Volume permission errors (macOS), ARM64 compatibility
• Per-tool sections (Airflow, OpenMetadata, Superset)
• Diagnostic commands (docker compose logs, docker stats, make health)
• "Reset Everything" section

Acceptance criteria

• Covers at least 10 common issues with solutions
• Includes diagnostic command reference
• Organized by category
• Linked from README