v1.7 - Perfai Security

Rebrands the action's Marketplace-facing metadata:

• name: Perfai Actions → Perfai Security
• description: Find & fix broken access control in AI-coded apps. Autonomously.
• branding.icon: trending-up → shield

(#17, merged earlier) plus the README usage example bumped to this tag (#18).

Fixes the stale GitHub Marketplace listing described in PerfAI-Inc/Perfai-Main-website#38.

Manual step still required: edit this release and tick "Publish this Action to the GitHub Marketplace" — that option isn't exposed via the API.