A 38-year-old woman presents to a community clinic complaining of progressive weakness over the past 36 hours. She initially reported blurred vision, difficulty focusing, and a persistent sensation of dry mouth, which she attributed to fatigue. This was followed by increasing difficulty speaking and swallowing, making her concerned. She then noticed a generalized weakness that started in her face and neck, making it hard to hold her head up, and has now spread downwards, affecting her upper limbs. She mentions that a week prior, she shared some homemade preserves, including green beans, with her family members, none of whom have reported similar symptoms. Her vital signs upon initial assessment are: temperature 36.80C, blood pressure 130/85 mmHg, pulse 78/min, respirations 16/min, and oxygen saturation 96% on room air. Physical examination reveals bilateral ptosis, sluggish pupillary response, and severely dysarthric speech. She exhibits generalized hypotonia, a profound decrease in facial muscle strength, and 3/5 strength in her proximal upper extremities with absent deep tendon reflexes. Distal strength appears relatively preserved initially. She is noted to be taking shallow breaths. Given the rapid progression of her symptoms, she is immediately referred to the nearest tertiary hospital for urgent admission. Identify the most likely diagnosis and outline the immediate critical management steps to mitigate further deterioration.