Release metadq 0.1.0

[keemgdeok]

Summary

• set the project version to 0.1.0
• point the Quick Start at the stable release asset
• disclose limited external Iceberg-user validation in the README
• move completed release gates out of the active roadmap

Verification

• Java 17 clean build and 38 automated tests
• Spotless and actionlint 1.7.7
• stable-version JAR checksum and doctor --demo guard
• release readiness already validated with Linux/macOS RC artifacts and MinIO/REST E2E

After this PR merges, tag v0.1.0. The release workflow will validate the exact JAR on Ubuntu and macOS before publishing it.