feat(booth): rework Active Sessions + pay/exit modal around barrier re-open

Move the audited barrier re-open out of the inline Active-Sessions row button
and into the modal, and turn the modal's dead-ends into useful views.

- Remove the inline per-row "Open barrier" button. Clicking a row opens the
  modal, which carries the action.
- Modal recognizes a closed-within-grace transient (found && !open &&
  withinGrace) and shows the session view + Open barrier instead of dead-ending
  on "already closed" — the exact case (paid, barrier unconfirmed) that needs a
  re-pulse. Server reopenBarrier guard unchanged.
- Active-Sessions rows show a live grace-remaining countdown badge
  (exited - M:SS, 1s tick off graceExpiresAt) via new formatCountdown helper.
- Settled sessions show the ACTUAL sum paid (new SessionLookup.paidMinor,
  summed across payment events) instead of a flat "PAID" badge.
- A fully-closed (grace-expired) session's modal is no longer a dead-end: it
  shows a read-only review view (figures + paid amount + entry/exit snapshot
  strip) for dispute/audit review, with no pay/exit/open controls.

i18n sq+en parity kept; web build/lint/test green.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/api.ts

@@ -1168,6 +1168,9 @@ export interface SessionLookup {
   paidAt: string | null;
   amountMinor: number | null;
   currency: string | null;
+  /** Amount actually PAID (sum of payment events), independent of what's owed now. */
+  paidMinor: number | null;
+  paidCurrency: string | null;
   withinGrace: boolean;
   graceExpiresAt: string | null;
   /** OVERSTAY: paid transient, walk-back grace expired, no exit — a new period began;