Unexpected €54k billing spike in 13 hours: Firebase browser key without API restrictions used for Gemini requests

Can you help me?
Opened up my billing page for GCP after my bank got in touch with me and found out that I had been charged for $6,486.81. I keep the account associated with GCP insanely low b/c I have always worried about this nightmare scenario. I wasted so many hours setting up alerts and budgets that i think i am done with cloud services and development in general. I promise to shut all accounts down after i get a refund.