Update template

PUT https://api.temporiza.com/api/Templates/{id}

Updates template metadata/content.

Business rules:

• id must be a valid UUID
• Returns 400 for invalid UUID or malformed JSON body
• Returns 404 when template does not exist
• Only provided fields are updated (name, description, is_active, fields)
• When fields is provided, each field is normalized with coordinates/dimensions and type metadata before persistence