Extends Huddle pins to static design artifacts so designers can collect client feedback on Figma exports, screenshots, PDF specs, mockups, and brand explorations - the SureFeedback/Pastel/MarkUp.io review use case.

Upload an image (JPEG/PNG/WebP) or PDF to a Hollahoop project; system creates a huddle_artifact (project_id, kind enum image|pdf, storage_key in Supabase Storage, page_count, dimensions, created_by). Reviewers open the artifact in a viewer that supports zoom, pan, multi-page navigation for PDFs, and click-to-pin at exact pixel coordinates. Pins reuse huddle_pins schema with anchor jsonb storing {x, y, page} for artifacts. Threaded comments, resolution status, and assignees all reuse the existing post infrastructure.

Sharing: each artifact gets a public review URL that can be sent to clients (gated by guest reviewer flow card for auth and integrity). Versioning: upload a new version of the same artifact and previous pins are preserved on the previous version with a "fixed in v2?" prompt. Out of scope: real-time collaborative cursors (later polish), Figma integration (separate card if demand exists).