Image placeholders

Intentional screenshot placeholders in documentation. Each row must match a current doc page and use descriptive alt text.

Doc	Image path	Alt text	Description	Status
user-guide/getting-started.md	../assets/images/user-guide/template-editor-opengraph-sidebar.png	Template editor sidebar with Open Graph image use case enabled and post title mapped to a text shape	CoverKit template editor: Open Graph use case on, mapping visible	placeholder
user-guide/templates.md	../assets/images/user-guide/import-template-modal.png	Import template modal showing dimension presets from CoverKit settings	Template list or editor: import-from-template flow with presets	placeholder

When a screenshot is captured, move the file under docs/assets/images/... and set status to captured. Remove the row when the placeholder is removed from the doc.