Refactor cron to call API via HTTP, capture base_url from browser

- meal-cron now runs send_reminders_cron.sh (simple wget loop, no DB mount)
- New /api/cron-tick endpoint handles all timezone logic server-side
- base_url captured from request.host_url when user saves ntfy settings,
  stored per-user — no APP_BASE_URL env var needed
- Cron endpoint protected by CRON_SECRET shared env var
- Removed send_reminders_cron.py, DB volume from cron container
- tests: 3 new cron-tick + base_url capture tests (69 total)

app.py

@@ -34,13 +34,14 @@ def create_app() -> Flask:
     def send_reminders_command(date, meal, base_url):
         """Send ntfy meal reminders to all users who have ntfy configured."""
         target_date = date and __import__("datetime").datetime.strptime(date, "%Y-%m-%d").date() or date.today()
-        app_base_url = base_url or os.environ.get("APP_BASE_URL", "http://localhost:5000")
+        fallback_url = base_url or os.environ.get("APP_BASE_URL", "http://localhost:5000")
 
         meal_types = ["lunch", "dinner"] if meal == "both" else [meal]
         total_sent = 0
 
         for household in get_all_households():
             for user in get_users_with_ntfy(household["id"]):
+                user_base_url = user.get("base_url") or fallback_url
                 for mt in meal_types:
                     ok = send_meal_reminder(
                         ntfy_url=user["ntfy_url"],
@@ -48,7 +49,7 @@ def create_app() -> Flask:
                         callback_token=user["callback_token"],
                         meal_type=mt,
                         for_date=target_date,
-                        app_base_url=app_base_url,
+                        app_base_url=user_base_url,
                     )
                     if ok:
                         total_sent += 1