refactor(bookings): simplify capacity tracking to use seats

Replace 'pax' booking mode with 'seat'
Consolidate inventory summary to track only seat counts
Update database schema and UI for seat-centric capacity

server/api/bookings/capacity.patch.ts

@@ -7,15 +7,15 @@ export default defineEventHandler(async (event) => {
   await requireRole(event, 'super_admin')
 
   const body = await readBody<{
-    totalTables?: number | string | null
+    totalSeats?: number | string | null
   }>(event)
 
   const input = parseBookingCapacityInput(body)
   const summary = await getBookingInventorySummary()
 
   assertBadRequest(
-    input.totalTables === null || (input.totalTables * 10) >= summary.soldCapacitySeats,
-    `Total tables cannot be lower than the currently sold capacity of ${summary.soldTables} tables and ${summary.soldSeats} seats`
+    input.totalSeats === null || input.totalSeats >= summary.soldSeats,
+    `Total seats cannot be lower than the currently sold count of ${summary.soldSeats} seats`
   )
 
   const settings = await updateBookingCapacitySettings(input)