feat(series): SeriesPage model + 0005 migration (unique image, ordered pages)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/test_series_model.py

@@ -0,0 +1,40 @@
+import pytest
+from sqlalchemy import select
+from sqlalchemy.exc import IntegrityError
+
+from backend.app.models import ImageRecord, TagKind
+from backend.app.models.series_page import SeriesPage
+from backend.app.services.tag_service import TagService
+
+pytestmark = pytest.mark.integration
+
+_SEQ = 0
+
+
+async def _img(db):
+    global _SEQ
+    _SEQ += 1
+    rec = ImageRecord(
+        path=f"/tmp/fc_sp_{_SEQ}.png", sha256=f"{_SEQ:064d}",
+        size_bytes=1, mime="image/png", origin="uploaded",
+    )
+    db.add(rec)
+    await db.flush()
+    return rec.id
+
+
+@pytest.mark.asyncio
+async def test_series_page_roundtrip_and_unique_image(db):
+    s = await TagService(db).find_or_create("Vol1", TagKind.series)
+    i1 = await _img(db)
+    db.add(SeriesPage(series_tag_id=s.id, image_id=i1, page_number=1))
+    await db.flush()
+    got = await db.scalar(
+        select(SeriesPage.page_number).where(SeriesPage.image_id == i1)
+    )
+    assert got == 1
+    # UNIQUE image_id: same image can't be a page twice (any series).
+    s2 = await TagService(db).find_or_create("Vol2", TagKind.series)
+    db.add(SeriesPage(series_tag_id=s2.id, image_id=i1, page_number=1))
+    with pytest.raises(IntegrityError):
+        await db.flush()