feat(shared): mark_attachment_viewed + view_once on AttachmentHandle

packages/shared/src/chat/attachments.ts

@@ -25,6 +25,16 @@ export interface AttachmentHandle {
   // base64-encoded — only readable via per-device envelope decrypt.
   keyB64: string;
   nonceB64: string;
+  /** View-once flag — set by sender on the encrypted envelope and mirrored
+   *  to `message_attachments.view_once` so the renderer can show a "tap to
+   *  view" tombstone and call the mark-viewed RPC on first open. */
+  viewOnce?: boolean;
+  /** ISO timestamp the first non-sender opened the attachment. Populated by
+   *  the mark-viewed RPC (server-authoritative); undefined until burnt. */
+  viewedAt?: string | null;
+  /** UUID of the first non-sender who viewed. Populated alongside `viewedAt`
+   *  by the mark-viewed RPC so the renderer can render attribution. */
+  viewedBy?: string | null;
 }
 
 export type CallEventStatus = 'ended' | 'missed' | 'declined';
@@ -256,6 +266,7 @@ export async function insertAttachmentRow(
     nonce: blobNonceHex,
     mime_type: handle.mimeType,
     size_bytes: handle.sizeBytes,
+    view_once: handle.viewOnce ?? false,
   };
   if (handle.width !== undefined) row.width = handle.width;
   if (handle.height !== undefined) row.height = handle.height;