[somebox]

Summary

• Replace the README board screenshot with the current dashboard and add the classroom-theme and relationship-detail screenshots from the Somebox post; reuse the matching current TUI capture.
• Bring the README in line with the v0.3.0 changelog: document cards release, the comment alias, tag-policy/default-board/searchable-field behavior, the full OpenAPI endpoint, and durable-event catch-up versus best-effort SSE.

Validation

• Checked all 27 README links and image targets; all relative paths exist and the external documentation/release links return HTTP 200.
• git diff --check passes. Documentation and image changes only; no Go tests run.