Per-artist "+N" accent pill on the artists directory and a "N new since
last visit" banner inside ArtistView. Counts new IMAGES (not posts) so
multi-image posts increment correctly.
- alembic 0034: artist_visit (artist_id PK, last_viewed_at NOT NULL).
Seeds every existing artist with last_viewed_at=NOW() so the badge
starts at 0 across the board — no noisy "5000 unseen images" on
first deploy.
- ArtistService.find_or_create autoseeds a visit row alongside new
artists, so freshly imported content doesn't read as unseen.
- ArtistService.overview reads pre-visit last_viewed_at, counts images
created since, then atomically UPSERTs last_viewed_at=NOW() via
postgres ON CONFLICT DO UPDATE (no SELECT-then-INSERT race per
reference_scalar_one_or_none_duplicates). Returns the pre-update
count as `unseen_count_at_visit` so the banner has data.
- ArtistDirectoryService.list_artists adds an `unseen_count` aggregate
to each card via LEFT JOIN artist_visit + conditional COUNT. NULL
last_viewed_at (artist created before this code shipped) defensively
counts as "never visited" → all images unseen.
- Frontend: ArtistCard renders an accent pill in the preview-strip
corner when unseen_count > 0 (capped at 99+); ArtistView shows a
closable v-alert banner on initial load when
unseen_count_at_visit > 0, re-arms on slug change.
Single-row-per-artist (no user_id) — rule #47 multi-user ACL is
aspirational; widens to (user_id, artist_id) PK when User lands, per
rule #22.
Scribe plan #597.
