feat: multi-pet client group booking (closes #10) (#31)

* feat: multi-pet client group booking (closes groombook/groombook#10) (GRO-27)

- Add appointment_groups table: links multiple appointments from one client visit
- Add group_id FK on appointments (nullable, backward-compatible)
- Add GET/POST/PATCH/DELETE /api/appointment-groups endpoints
  - POST creates group record + one appointment per pet atomically (with conflict checks)
  - DELETE soft-cancels all appointments in the group
- Add GroupBooking.tsx page at /group-bookings with:
  - Dynamic pet-slot form (min 2 pets, each with their own groomer/service/end time)
  - Auto-calculates end time from service duration
  - Group card list showing all pets, groomers, and statuses side-by-side
  - Client filter and cancel-all action
- Wire into nav and routing in App.tsx
- Export AppointmentGroup type; add groupId field to Appointment type

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

* fix: remove eslint-disable for uninstalled react-hooks plugin; remove unused clientMap (GRO-27)

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

---------

Co-authored-by: Groom Book CTO <cto@groombook.app>
Co-authored-by: Paperclip <noreply@paperclip.ing>

packages/db/src/schema.ts

@@ -102,6 +102,18 @@ export const recurringSeries = pgTable("recurring_series", {
   createdAt: timestamp("created_at").notNull().defaultNow(),
 });
 
+// appointmentGroups links multiple appointments from the same client visit.
+// Each pet in the group gets its own appointment row with its own groomer.
+export const appointmentGroups = pgTable("appointment_groups", {
+  id: uuid("id").primaryKey().defaultRandom(),
+  clientId: uuid("client_id")
+    .notNull()
+    .references(() => clients.id, { onDelete: "restrict" }),
+  notes: text("notes"),
+  createdAt: timestamp("created_at").notNull().defaultNow(),
+  updatedAt: timestamp("updated_at").notNull().defaultNow(),
+});
+
 export const appointments = pgTable("appointments", {
   id: uuid("id").primaryKey().defaultRandom(),
   clientId: uuid("client_id")
@@ -127,6 +139,10 @@ export const appointments = pgTable("appointments", {
     onDelete: "set null",
   }),
   seriesIndex: integer("series_index"),
+  // Multi-pet group booking: links this appointment to others in the same visit
+  groupId: uuid("group_id").references(() => appointmentGroups.id, {
+    onDelete: "set null",
+  }),
   createdAt: timestamp("created_at").notNull().defaultNow(),
   updatedAt: timestamp("updated_at").notNull().defaultNow(),
 });