Your wife went ahead and made an optional purchase of a pet, knowing that it absolutely terrified you. She made this purchase with no consideration at all of how much emotional pain this would inflict on you.
This is a big deal. You are right to be angry. I don't believe in a loving relationship a spouse would go ahead and do such a thing. Even though you don't indicate this in your question, there are more problems going on in your relationship.
I have some understanding of how wrong her action is because my best friend, a guy I've known since grade school, is absolutely terrified of dogs. Forcing my friend to "confront his fear" by forcing a dog on him would be incredibly cruel, and totally useless. I can't imagine doing such a thing to a friend, much less a spouse or partner.
You should get individual counseling. Not to help you with any phobias, but so you can discuss what's going on in your marriage with a neutral third party. From there you can make some decisions about what to do next. Having someone to discuss this with will help with coming up with some concrete options instead of just feeling helpless and terrified.