Add a `template remove --purge` option

[Nanle-code]

Add a --purge flag to starforge template remove that deletes both the registry entry and any cached or downloaded template assets. Without --purge, only the registry metadata should be removed. This provides a safe way to clean up local template storage.

[dextro172-ui]

@dextro172-ui has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

i would love to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @dextro172-ui to this issue.

[drips-wave]

Congratulations, @dextro172-ui! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @dextro172-ui: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊