feat(reader): a Takeout video the catalog learns later is marked watched then; the import's status

A watched video the catalog did not know at import time waits in `takeout_items`. The Shorts job now
settles those rows right after its probe (the only place a video's Short-ness becomes known), every
user's, a commit each: `reader.takeout.apply_waiting`, its count in the job's result.

`GET /api/takeout` is what the settings page reads: the user's last import run (`jobruns.last_run`)
and the kept videos by kind and outcome, "waiting" for one not known yet.

backend/app/reader/queries.py

@@ -422,3 +422,30 @@ def takeout_outcomes(db: Session, user: User) -> dict[tuple[str, str | None], in
         .group_by(TakeoutItem.kind, TakeoutItem.outcome)
     ).all()
     return {(kind, outcome): n for kind, outcome, n in rows}
+
+
+def takeout_summary(db: Session, user: User) -> dict[str, dict[str, int]]:
+    """The user's kept Takeout videos by kind and outcome, for their settings page: `{"watched":
+    {"watched": n, "short": n, "waiting": n, …}, "watch_later": {…}}` — the import's outcome words,
+    "waiting" for a video not known yet."""
+    out: dict[str, dict[str, int]] = {kind.value: {} for kind in TakeoutKind}
+    for (kind, outcome), n in takeout_outcomes(db, user).items():
+        out[kind][outcome or "waiting"] = n
+    return out
+
+
+def takeout_users_ready(db: Session) -> list[int]:
+    """Every user with a waiting "watched" row whose video is now known and probed for Shorts: the
+    rows a later run of the Shorts probe made ready."""
+    return list(
+        db.execute(
+            select(TakeoutItem.user_id)
+            .join(Video, Video.id == TakeoutItem.video_id)
+            .where(
+                TakeoutItem.kind == TakeoutKind.WATCHED,
+                TakeoutItem.outcome.is_(None),
+                Video.shorts_probed,
+            )
+            .distinct()
+        ).scalars()
+    )