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>

apps/web/src/routes/dashboard/subscription/index.tsx

@@ -174,8 +174,6 @@ export function SubscriptionPage() {
 
   // ─── Search-param-driven flags (read once) ─────────────────────────────────
   const [welcome] = useState(() => search.welcome === "1");
-  const [initialRef] = useState(() => search.ref ?? null);
-  const hasAppliedRefRef = useRef(false);
   const stripeResultRef = useRef(false);
 
   // ─── Stepper state ─────────────────────────────────────────────────────────
@@ -299,12 +297,6 @@ export function SubscriptionPage() {
     }
   }, [subscription, currentPlanKey]);
 
-  useEffect(() => {
-    if (!initialRef || !subData || hasAppliedRefRef.current) return;
-    hasAppliedRefRef.current = true;
-    api.post("/referrals/apply", { code: initialRef.toUpperCase().trim() }).catch(() => {});
-  }, [initialRef, subData]);
-
   useEffect(() => {
     if (!welcome || !subData || hasFiredRef.current) return;
     if (!eligibleForTrial) {