Manage birthdays with natural language. Store birthdays in /home/clawd/clawd/data/birthdays.md, get upcoming reminders, calculate ages. Use when the user mentions birthdays, wants to add/remember someone's birthday, check upcoming birthdays, or asks about someone's age/birthday. Understands phrases like "X hat am DD.MM. Geburtstag", "Wann hat X Geburtstag?", "Nächste Geburtstage".