feat: appointment confirmation and cancellation (GH #98, GRO-153)

Add customer confirmation/cancellation flow for appointments:

- DB migration (0013): add confirmation_status, confirmed_at, cancelled_at,
  confirmation_token to appointments table with index on token column
- schema.ts + factories.ts + types: expose new columns and ConfirmationStatus type
- GET /api/book/confirm/:token — tokenized confirm via email link (redirects)
- GET /api/book/cancel/:token — tokenized cancel via email link, single-use token
- POST /api/appointments/:id/confirm — portal/staff confirm endpoint
- POST /api/appointments/:id/cancel — portal/staff cancel endpoint
- Reminder emails now include Confirm/Cancel CTA buttons with tokenized links
- Reminder service generates confirmation token if missing before sending
- Staff calendar shows confirmation status indicator on appointment cards
  and in the detail modal (confirmed ✓ / customer cancelled ✗)
- /booking/confirmed, /booking/cancelled, /booking/error redirect pages
- 23 new unit tests covering all new endpoints and edge cases

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/types/src/index.ts

@@ -8,6 +8,8 @@ export type AppointmentStatus =
   | "cancelled"
   | "no_show";
 
+export type ConfirmationStatus = "pending" | "confirmed" | "cancelled";
+
 export type ClientStatus = "active" | "disabled";
 
 export interface Client {
@@ -104,6 +106,10 @@ export interface Appointment {
   seriesId: string | null;
   seriesIndex: number | null;
   groupId: string | null;
+  confirmationStatus: ConfirmationStatus;
+  confirmedAt: string | null;
+  cancelledAt: string | null;
+  confirmationToken: string | null;
   createdAt: string;
   updatedAt: string;
 }