Add plugin trust store configuration

[Nanle-code]

Add a configurable plugin trust store or allowlist of trusted plugin sources. Store trusted domains/URLs in the CLI config, and use it when starforge plugin install evaluates plugin source risk. This makes plugin installation safer in organizations and shared environments.

[whitezaddy]

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

Hi Maintainer! i sincerely wish to work on this. pls assign.

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

[drips-wave]

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

🧑‍💻 @whitezaddy: 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.

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