Implements groombook/groombook#12 — track which staff worked on each
pet and calculate tip distribution based on who was involved.
Changes:
- DB: Add bather_staff_id to appointments (optional secondary staff)
- DB: Add invoice_tip_splits table (per-staff tip share ledger)
- API: appointments POST/PATCH accept batherStaffId
- API: GET /invoices/:id now includes tipSplits[]
- API: POST /invoices/:id/tip-splits — saves tip distribution
- API: GET /reports/tip-splits — payroll summary of tip earnings
- Frontend: Bather/Assistant select on New Appointment form
- Frontend: Tip Distribution section in Invoice Detail modal
- Auto-populates 70%/30% split when bather is assigned
- Editable percentages before payment; saved on Mark as Paid
- Displays recorded splits on paid invoices
Co-Authored-By: Paperclip <noreply@paperclip.ing>
Groom Book CTO