feat: delay show rotation during live recording window

Decouple the like-window boundary (Wed 10pm ET) from when the system
rotates to a new show. NTR_SHOW_ROTATION_DELAY_HOURS=2 keeps the
previous week's show visible during the ~2 hour recording, then creates
the new show at midnight.

Made-with: Cursor

src/ntr_fetcher/week.py

@@ -36,3 +36,23 @@ def get_show_week(
     week_end_utc = (candidate + timedelta(days=7)).astimezone(timezone.utc).replace(tzinfo=timezone.utc)
 
     return week_start_utc, week_end_utc
+
+
+def get_current_show_week(
+    now_utc: datetime,
+    show_day: int = SHOW_DAY_DEFAULT,
+    show_hour: int = SHOW_HOUR_DEFAULT,
+    rotation_delay_hours: float = 0,
+) -> tuple[datetime, datetime]:
+    """Return the show week that should be treated as "current" right now.
+
+    When *rotation_delay_hours* > 0 the switchover to a new show is postponed
+    by that many hours after the like-window boundary.  During the gap the
+    previous week's show remains current so the host can view it while
+    recording.  Likes made during the gap are collected by the new show once
+    it rotates in.
+    """
+    if rotation_delay_hours <= 0:
+        return get_show_week(now_utc, show_day, show_hour)
+    effective_now = now_utc - timedelta(hours=rotation_delay_hours)
+    return get_show_week(effective_now, show_day, show_hour)