docs+fix(#173): API cards sans couleur ; alignement evenements_agenda

Couleur = mapping front (type_code). Spec §32 / mini-spec bulles.
Rebase sur develop (#205).

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/modules/cards/cards.service.spec.ts

@@ -80,7 +80,6 @@ describe('CardsService (#194)', () => {
       audience_resolver: 'couple_parents',
       response_mode: CardResponseModeType.ACCEPT_REFUSE,
       retention_days: 14,
-      couleur: 'lavender',
     });
     amChildrenRepo.findOne.mockResolvedValue({
       id: 'pl-1',