Todo: scheduled Discord notifications via cron

- cron/todo_notify.php: checks every minute for tasks due now and sends
  Discord reminder (⏰) only when due_date+due_time is reached
- No immediate notification when due_time is set (cron handles it)
- Immediate notification still fires for tasks without a due_time
- notified column tracks whether reminder was already sent
- Resets notified=0 when a task is edited (new time picked)
- Cron runs via: docker exec househub php /var/www/html/cron/todo_notify.php

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker/schema_family.sql

@@ -335,6 +335,7 @@ CREATE TABLE IF NOT EXISTS pf_todos (
   notes      TEXT DEFAULT NULL,
   due_date   DATE DEFAULT NULL,
   due_time   TIME DEFAULT NULL,
+  notified   TINYINT(1) DEFAULT 0,
   priority   ENUM('none','low','medium','high') DEFAULT 'none',
   done       TINYINT(1) DEFAULT 0,
   done_at    DATETIME DEFAULT NULL,