feat(bookmarks): bulk-remove consumed release bookmarks

[obrien-k]

What

BookmarksPage is fully read-only today (verified 2026-07-04): once a member has consumed a bookmarked release there is no way to clear it from the list short of unbookmarking one by one. Power users accumulate large bookmark lists as consumption queues; a one-click "remove the ones I've already consumed" keeps the queue meaningful.

Scope

• DELETE /api/bookmarks/releases/consumed — removes the caller's release bookmarks whose release they hold a consumption record for.
• Paired stellar-ui work: a bulk button on BookmarksPage (file the ui issue when this is picked up, per the contract-hygiene convention).

Design blueprint exists (2026-07-04 parity deep dive, item J2); its detail lands on this issue when the blueprint corpus is transplanted.

Surfaced by the 2026-07-08 parity harvest.

[obrien-k]

Blueprint detail (deep-scrub item J2), as promised in the body:

• API: DELETE /api/bookmarks/releases/consumed — deleteMany of BookmarkRelease where the release has a COMPLETED DownloadAccessGrant for the viewer; returns {removed: n}.
• UI: "Remove consumed" button on the BookmarksPage Releases tab; bookmarkApi.ts mutation invalidating the releases tag.
• Naming note: the pre-existing pages/private/snatch/ directory in stellar-ui carries non-sanctioned naming — flag a separate ui rename issue at pickup rather than extending it.