Show shift type label for both weekend shifts in notifications

Night shift notifications on weekends were missing the type label,
making them ambiguous. Also fix schedule post text fallback to use
this_monday instead of now for the start date.

src/shared/python/shared/blocks.py

@@ -131,7 +131,9 @@ def build_shift_change_message(
     dt = datetime.strptime(date_str, "%Y-%m-%d")
     day_label = dt.strftime("%A, %b %-d")
     type_label = (
-        f" ({SHIFT_LABELS.get(shift_type, shift_type)})" if shift_type == "day" else ""
+        f" ({SHIFT_LABELS.get(shift_type, shift_type)})"
+        if dt.strftime("%A") in WEEKEND_DAYS
+        else ""
     )
 
     if action == "picked_up":

src/slack-bot/app.py

@@ -252,7 +252,7 @@ def create_app(
                 channel=channel,
                 ts=post["message_ts"],
                 blocks=blocks,
-                text=f"After-Hours Schedule — {now.strftime('%b %-d')} to {end_date.strftime('%b %-d')}",
+                text=f"After-Hours Schedule — {this_monday.strftime('%b %-d')} to {end_date.strftime('%b %-d')}",
             )
         except Exception:
             logger.warning("Could not update schedule post", exc_info=True)