feat(referrals): rework reward engine + email-verified landing

Reward engine:
- Recurring milestones (every 3 → +7d, every 5 → +14d) instead of one-time
  tiers capped at 5; idempotent + transactional grants serialised per
  referrer so concurrent qualifications can't double-count.
- Rewards now gated on the referred user's email verification
  (afterEmailVerification hook); already-verified referees (OAuth) qualify
  at apply time.
- Reward days banked as users.referral_credit_days when the referrer has no
  live subscription, consumed on next trial start / activation (no more
  silently lost rewards).
- Accurate cumulative rewardDays in stats; getMyReferrals returns referee
  name/masked email/status.

Hardening / cleanup:
- onConflictDoNothing makes apply idempotent (no unhandled unique violation).
- Anti-fraud: normalizeEmail blocks self-referral via gmail dot/+tag aliases.
- Collision-safe referral code generation at signup.
- Single apply path (welcome onboarding modal); removed duplicate calls in
  register + subscription pages. Input validation on the apply code.

Email verification UX:
- Verification link now lands on a dedicated /email-verified confirmation
  page instead of the deep-linked VIN/search page.

Schema: referrals.status + qualified_at, users.referral_credit_days (0009).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

packages/shared/src/index.ts

@@ -44,7 +44,14 @@ export { paginationSchema } from "./schemas/pagination.js";
 
 // Constants
 export { VIN_REGEX, EMAIL_REGEX, OEM_CODE_REGEX } from "./constants/regex.js";
-export { PLANS, REFERRAL_REWARDS, CURRENCY, FULL_PLAN_BRAND_LIMIT } from "./constants/plans.js";
+export {
+  PLANS,
+  REFERRAL_REWARDS,
+  CURRENCY,
+  FULL_PLAN_BRAND_LIMIT,
+  referralRewardForCount,
+  referralTotalRewardDays,
+} from "./constants/plans.js";
 export { ERROR_CODES } from "./constants/error-codes.js";
 export type { ErrorCode } from "./constants/error-codes.js";
 
@@ -62,4 +69,5 @@ export {
   formatDateTime,
   slugify,
   generateReferralCode,
+  normalizeEmail,
 } from "./utils/formatters.js";