FAS 1b: Progressive onboarding (3-layer flow)

- Add PROGRESSIVE_ONBOARDING feature flag to KNOWN_FLAGS
- Add onboarding_step column to users table (a/b/c)
- New backend endpoints:
  - GET /v1/onboarding/status – check current step + feature flag
  - POST /v1/onboarding/quick-start – complete Step A (goal + precision)
  - POST /v1/onboarding/complete-b – complete Step B (diet, allergens, household)
  - POST /v1/onboarding/complete-c – complete Step C (health profile)
  - POST /v1/onboarding/skip – GDPR-friendly skip
- Refactor mobile onboarding screen into 3 progressive layers
- Update auth store with onboardingStep state
- Update tab layout to only block on Step A
- Update registration to set onboardingStep='a'
- Add i18n keys for Step B/C titles across all 12 locales
- Add Zod validation schemas (quickStartInputSchema, onboardingStatusSchema)
- Add tests for validation and feature flag
- Preserve existing /v1/me/onboarding for backward compatibility
- Migration: 0004_progressive_onboarding.sql

apps/api/src/server.ts

@@ -25,6 +25,7 @@ import { adminAnalyticsRoutes } from "./routes/admin-analytics.js";
 import { adminReleaseGateRoutes } from "./routes/admin-release-gates.js";
 import { adminWorkersRoutes } from "./routes/admin-workers.js";
 import { analyticsRoutes } from "./routes/analytics.js";
+import { onboardingRoutes } from "./routes/onboarding.js";
 
 declare module "fastify" {
   interface FastifyInstance {
@@ -88,6 +89,7 @@ export async function buildServer(config: AppConfig) {
   await app.register(adminReleaseGateRoutes);
   await app.register(adminWorkersRoutes);
   await app.register(analyticsRoutes);
+  await app.register(onboardingRoutes);
 
   return app;
 }