Update Ask Snowy agent settings

Changes the brand's Ask Snowy settings. Only the fields sent change. customInstructions (up to 2000 characters) are house rules added to every chat; responseStyle is concise, balanced, detailed; responseLanguage is "auto" or a language code like "en" or "pt-BR". The booleans switch Snowy's write actions, knowledge base, brand memory and automatic memory on or off for every member. Needs admin or owner access.