feat: wire step_reminder into runner, admin, and scheduler (Fri 16:00 PT)

backend/app/scheduler/__main__.py

@@ -7,6 +7,7 @@ Weekly cadence (America/Los_Angeles):
   Fri 02:00 — scrape   (Lucky weekend prices live by ~midnight)
   Fri 05:00 — generate (fresh grocery data)
   Fri 06:00 — email    (per-voter approval links)
+  Fri 16:00 — reminder (nudge non-voters, 1h before deadline)
   Fri 17:00 — deadline (pending items resolved per family policy)
   Fri 18:00 — finalize (shopping-list email)
 """
@@ -45,6 +46,12 @@ scheduler.add_job(
     id="weekly_email",
     name="Weekly email (Fri 06:00 PT)",
 )
+scheduler.add_job(
+    lambda: run_step("reminder"),
+    CronTrigger(day_of_week="fri", hour=16, minute=0, timezone=TZ),
+    id="weekly_reminder",
+    name="Weekly reminder (Fri 16:00 PT)",
+)
 scheduler.add_job(
     lambda: run_step("deadline"),
     CronTrigger(day_of_week="fri", hour=17, minute=0, timezone=TZ),