feat(gallery): composable scroll filter (multi-tag AND, media, sort)

Phase 1 backend for the gallery filter bar. Extends scroll/timeline/jump
from a single mutually-exclusive filter to a composable one:

- tag_ids: image must carry ALL of them (one correlated EXISTS per tag —
  AND, no row multiplication), replacing the single-tag JOIN.
- artist_id composes with tags; media_type ('image'|'video') narrows by
  mime; post_id stays the exclusive post-detail path.
- sort ('newest'|'oldest') flips the effective_date/id cursor comparison
  and ordering; the cursor value is unchanged (direction comes from the
  request). jump_cursor honors sort too.
- Shared _apply_scope helper applied across scroll/timeline/jump so the
  timeline sidebar reflects the filtered set. API _parse_filters parses
  tag_id (comma list), artist_id, media, sort.

Tests: multi-tag AND, media filter, sort reversal (service + API);
post_id-excludes-others; single tag_id back-compat.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_api_gallery.py

@@ -59,3 +59,21 @@ async def test_jump_requires_year_month(client):
 async def test_image_detail_404_when_missing(client):
     resp = await client.get("/api/gallery/image/99999")
     assert resp.status_code == 404
+
+
+@pytest.mark.asyncio
+async def test_scroll_sort_param_reverses(client, db):
+    await _seed(db, 3)
+    newest = await (await client.get("/api/gallery/scroll?limit=10&sort=newest")).get_json()
+    oldest = await (await client.get("/api/gallery/scroll?limit=10&sort=oldest")).get_json()
+    ids_new = [i["id"] for i in newest["images"]]
+    ids_old = [i["id"] for i in oldest["images"]]
+    assert ids_old == list(reversed(ids_new))
+
+
+@pytest.mark.asyncio
+async def test_scroll_media_param(client, db):
+    await _seed(db, 2)  # only image/jpeg seeded
+    resp = await client.get("/api/gallery/scroll?limit=10&media=video")
+    assert resp.status_code == 200
+    assert (await resp.get_json())["images"] == []

tests/test_gallery_provenance_filter.py

@@ -81,10 +81,10 @@ async def test_scroll_artist_id_filter(db):
 
 
 @pytest.mark.asyncio
-async def test_mutually_exclusive_filters_raise(db):
+async def test_post_id_excludes_other_filters(db):
     svc = GalleryService(db)
     with pytest.raises(ValueError):
-        await svc.scroll(cursor=None, limit=10, tag_id=1, post_id=2)
+        await svc.scroll(cursor=None, limit=10, tag_ids=[1], post_id=2)
 
 
 @pytest.mark.asyncio

tests/test_gallery_service.py

@@ -87,7 +87,7 @@ async def test_scroll_with_tag_filter(db):
     )
 
     svc = GalleryService(db)
-    page = await svc.scroll(cursor=None, limit=10, tag_id=tag.id)
+    page = await svc.scroll(cursor=None, limit=10, tag_ids=[tag.id])
     assert len(page.images) == 1
     assert page.images[0].id == images[0].id
 
@@ -272,3 +272,53 @@ async def test_get_image_with_tags_includes_posted_at_when_present(db):
     assert payload["posted_at"] is not None
     # Image's own created_at is still surfaced separately.
     assert payload["created_at"] != payload["posted_at"]
+
+
+@pytest.mark.asyncio
+async def test_scroll_multi_tag_and(db):
+    images = await _seed_images(db, 5)
+    a = Tag(name="aa", kind=TagKind.general)
+    b = Tag(name="bb", kind=TagKind.general)
+    db.add_all([a, b])
+    await db.flush()
+    # images[0] carries BOTH tags; images[1] carries only a.
+    await db.execute(image_tag.insert().values([
+        {"image_record_id": images[0].id, "tag_id": a.id, "source": "manual"},
+        {"image_record_id": images[0].id, "tag_id": b.id, "source": "manual"},
+        {"image_record_id": images[1].id, "tag_id": a.id, "source": "manual"},
+    ]))
+    svc = GalleryService(db)
+    both = await svc.scroll(cursor=None, limit=10, tag_ids=[a.id, b.id])
+    assert [i.id for i in both.images] == [images[0].id]  # AND: only the both-tagged
+    just_a = await svc.scroll(cursor=None, limit=10, tag_ids=[a.id])
+    assert {i.id for i in just_a.images} == {images[0].id, images[1].id}
+
+
+@pytest.mark.asyncio
+async def test_scroll_media_filter(db):
+    imgs = await _seed_images(db, 2)  # image/jpeg
+    vid = ImageRecord(
+        path="/images/test/v.mp4", sha256="v" * 64, size_bytes=1,
+        mime="video/mp4", width=1, height=1,
+        origin="imported_filesystem", integrity_status="unknown",
+    )
+    vid.created_at = _now()
+    vid.effective_date = vid.created_at
+    db.add(vid)
+    await db.flush()
+    svc = GalleryService(db)
+    vids = await svc.scroll(cursor=None, limit=10, media_type="video")
+    assert [i.id for i in vids.images] == [vid.id]
+    pics = await svc.scroll(cursor=None, limit=10, media_type="image")
+    assert {i.id for i in pics.images} == {i.id for i in imgs}
+
+
+@pytest.mark.asyncio
+async def test_scroll_sort_oldest_reverses_order(db):
+    images = await _seed_images(db, 4)  # images[0] newest ... images[3] oldest
+    svc = GalleryService(db)
+    newest = await svc.scroll(cursor=None, limit=10)
+    oldest = await svc.scroll(cursor=None, limit=10, sort="oldest")
+    newest_ids = [i.id for i in newest.images]
+    assert newest_ids[0] == images[0].id
+    assert [i.id for i in oldest.images] == list(reversed(newest_ids))