Open and close a parking session at the gate

A session is the time a vehicle is in your facility — opens at entry, closes at exit, charges accumulate in between.

Open a session (at the gate):
1. /parking → Sessions tab → "Open session" (or auto-triggered by ALPR / gate scanner integration)
2. **Plate number** (or scan a reservation QR / pass)
3. **Lot + zone** auto-detected from the gate, override if needed
4. Start time = now
5. Save → gate opens; session is live in the dashboard

If the vehicle has a reservation, the open-session step looks it up and binds the session to it (no separate charge — the reservation already prepaid the time).

Close a session (at exit):
1. Sessions tab → find by plate (Wally: `parking_lookupByPlate`)
2. "Close session"
3. Charge computed from rate plan × duration, minus any validations or prepaid reservation amount
4. Customer pays at the gate kiosk, in-app, or auto-charged if a payment method is on file
5. Gate opens; session moves to History

Wally tool `parking_findOpenSpaces` returns current open capacity by lot/zone — useful for digital signage and dynamic routing.