WrenchStrike: Mechanic Invoice

Customers can now sign to approve an estimate — right on your phone, before the work starts. The signature prints on the invoice. If they approved by phone or text instead, record that too. Once an estimate is approved, its line items lock so the agreed price can't drift. Unlock it and the signature is cleared, so everyone knows a re-approval is needed. Sent estimates now show a "Sent" date, and if the customer hasn't answered in 3 days, WrenchStrike nudges you with a one-tap "Text again." Also in this update: one shared vehicle editor with VIN decode everywhere, phone numbers formatted and validated, a single Warranty field plus a separate invoice footer, and sharper job titles like "Mike · 2018 Camry."