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

packages/database/src/schema/users.ts

@@ -39,6 +39,8 @@ export const users = pgTable(
     locale: text("locale").notNull().default("sv-SE"),
     precisionMode: precisionModeEnum("precision_mode").notNull().default("simple"),
     onboardingCompleted: boolean("onboarding_completed").notNull().default(false),
+    /** Progressive onboarding step: a=immediate value, b=after first value, c=completed (spec FAS 1b). */
+    onboardingStep: text("onboarding_step").notNull().default("a"),
     deletedAt: timestamp("deleted_at", { withTimezone: true }),
     createdAt: createdAt(),
     updatedAt: updatedAt(),