Mood is an optional label+emoji string (e.g. "relaxed 😌") on thoughts.
Users can define up to 8 custom moods in profile settings.
Mood federates via AP Note JSON and displays on thought cards.
DB→domain→API→AP→frontend end-to-end. Fields stored as
JSONB, exposed via PATCH /users/me, serialized as AP
PropertyValue attachment. Editor in federation settings,
display on profile card.
