feat: recurring appointments with cascading change propagation (#28)

* feat: recurring appointments with cascading change propagation

Implements GitHub issue #9 — recurring appointment scheduling with
configurable frequency and cascade edit/cancel options.

Changes:
- DB: add `recurring_series` table (frequency_weeks) and series_id /
  series_index columns on appointments (migration 0003)
- API POST /appointments: accepts optional `recurrence` object
  (frequencyWeeks + count) that creates a full series in one transaction
- API PATCH /appointments/🆔 new `cascadeMode` field
  (this_only | this_and_future | all) applies time-delta shifts and
  field updates across the series
- API DELETE /appointments/🆔 new `?cascade=` query param cancels
  this_only / this_and_future / all series members
- Frontend: booking form gains a "Recurring appointment" checkbox with
  frequency and count pickers; calendar chips show a ↻ recurring label;
  detail modal shows "Recurring series" badge and a cascade-delete radio
  picker for series appointments

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

* fix: resolve TypeScript errors in recurring appointments route

Guard against possibly-undefined results from Drizzle .returning()
destructuring — use indexed access + explicit null checks instead of
array destructuring for the recurring_series insert, and add an early
throw when the series or first appointment row is missing.

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

@@ -92,6 +92,13 @@ export const staff = pgTable("staff", {
   updatedAt: timestamp("updated_at").notNull().defaultNow(),
 });
 
+export const recurringSeries = pgTable("recurring_series", {
+  id: uuid("id").primaryKey().defaultRandom(),
+  // How many weeks between each appointment in the series
+  frequencyWeeks: integer("frequency_weeks").notNull(),
+  createdAt: timestamp("created_at").notNull().defaultNow(),
+});
+
 export const appointments = pgTable("appointments", {
   id: uuid("id").primaryKey().defaultRandom(),
   clientId: uuid("client_id")
@@ -112,6 +119,11 @@ export const appointments = pgTable("appointments", {
   notes: text("notes"),
   // Override price at time of booking (null = use service base price)
   priceCents: integer("price_cents"),
+  // Recurring series support
+  seriesId: uuid("series_id").references(() => recurringSeries.id, {
+    onDelete: "set null",
+  }),
+  seriesIndex: integer("series_index"),
   createdAt: timestamp("created_at").notNull().defaultNow(),
   updatedAt: timestamp("updated_at").notNull().defaultNow(),
 });