feat(30-01): create onboarding route with Zod validation and register

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/shared/schemas.ts

@@ -153,3 +153,8 @@ export const changeEmailSchema = z.object({
 export const deleteAccountSchema = z.object({
 	confirmation: z.literal("DELETE"),
 });
+
+// Onboarding schemas
+export const completeOnboardingSchema = z.object({
+	globalItemIds: z.array(z.number().int().positive()).max(50),
+});