ecaca35977
Make the admin Feedback section a real inbox.
* DB: feedback.read_at column (schema + idempotent migration).
* API: feedback list returns read_at; POST /api/admin/feedback/{id}/read
{read} toggles it; DELETE /api/admin/feedback/{id} removes a message
(both admin-gated). admin_stats gains feedback_unread; the Attention strip
and the tab badge now count UNREAD, not total.
* Frontend: unread messages are highlighted with an accent rail + dot; an
Unread filter joins the category chips; each message has Mark read/unread
and Delete (confirm), with optimistic updates that revert on failure.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>