fix(db): remove dedup DELETE and use ON CONFLICT (name) for idempotent services seed

The dedup DELETE was causing two problems:
1. FK violation (GRO-365) — deleting services referenced by appointments
2. Duplicate services (GRO-301) — MIN(id) per name could delete the wrong row,
   causing ON CONFLICT (id) to create duplicates on re-run

Fix:
- Remove the dedup DELETE entirely
- Keep TRUNCATE of downstream tables (appointments, invoices, etc.) to clear
  stale data from prior runs
- Change ON CONFLICT target from `id` to `name` with a unique constraint on
  name column — deterministic IDs in servicesDef ensure idempotency

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

packages/db/src/schema.ts

@@ -141,7 +141,7 @@ export const pets = pgTable("pets", {
 
 export const services = pgTable("services", {
   id: uuid("id").primaryKey().defaultRandom(),
-  name: text("name").notNull(),
+  name: text("name").notNull().unique(),
   description: text("description"),
   basePriceCents: integer("base_price_cents").notNull(),
   durationMinutes: integer("duration_minutes").notNull(),