Consolidate WEEKEND_DAYS and fix weekday pickup button labels

Import WEEKEND_DAYS from shared.schedule instead of redefining in
blocks.py and weekly-post/app.py. Gate pickup button day/night
labels on weekends only, matching all other display surfaces.

src/shared/python/shared/blocks.py

@@ -3,9 +3,9 @@
 from datetime import datetime, timedelta
 from zoneinfo import ZoneInfo
 
-EASTERN = ZoneInfo("America/New_York")
+from shared.schedule import WEEKEND_DAYS
 
-WEEKEND_DAYS = {"Saturday", "Sunday"}
+EASTERN = ZoneInfo("America/New_York")
 
 
 SHIFT_LABELS = {
@@ -97,14 +97,15 @@ def build_week_schedule(schedule, start_date: datetime | None = None) -> list[di
         elements = []
         for date_str, shift_type in open_shifts:
             dt = datetime.strptime(date_str, "%Y-%m-%d")
-            label = "Day" if shift_type == "day" else "Night"
+            day_name = dt.strftime("%A")
+            label = f" {SHIFT_LABELS[shift_type]}" if day_name in WEEKEND_DAYS else ""
             action_suffix = "_day" if shift_type == "day" else ""
             elements.append(
                 {
                     "type": "button",
                     "text": {
                         "type": "plain_text",
-                        "text": f"Pick up {dt.strftime('%a %b %-d')} {label}",
+                        "text": f"Pick up {dt.strftime('%a %b %-d')}{label}",
                     },
                     "action_id": f"pickup_{date_str}{action_suffix}",
                     "style": "primary",

src/weekly-post/app.py

@@ -11,7 +11,7 @@ import boto3
 from slack_sdk import WebClient
 
 from shared.blocks import build_pay_summary_blocks, build_week_schedule
-from shared.schedule import FALLBACK_EXTENSION, ShiftSchedule
+from shared.schedule import FALLBACK_EXTENSION, WEEKEND_DAYS, ShiftSchedule
 from shared.secrets import get_secret
 
 logger = logging.getLogger()
@@ -30,9 +30,6 @@ DAY_ORDER = [
 ]
 
 
-WEEKEND_DAYS = {"Saturday", "Sunday"}
-
-
 def _add_shift_to_pay(schedule, breakdown, totals, date, day_name, shift_type="night"):
     """Resolve a shift and add it to the pay breakdown if assigned."""
     date_str = date.strftime("%Y-%m-%d")