feat(credits): remove free $5 credit for new users

[kilo-code-bot]

Summary

• Disables the $5 automatic welcome credit that was granted to new users who pass Turnstile + Stytch validation during signup.
• handleSignupPromotion() in src/lib/stytch.ts is now a no-op — it retains the function signature for backward compatibility (called from account-verification/page.tsx) but no longer grants any credits.
• The automatic-welcome-credits promo category in src/lib/promoCreditCategories.ts has its amount_usd set to 0 as a belt-and-suspenders safeguard.
• The first-day welcome notification ("We added $5 to your balance…") in src/lib/notifications.ts is disabled since it no longer applies to new users.
• Existing users who already received the credit are unaffected — no retroactive changes.

Verification

• pnpm typecheck — passes clean across all 29 workspace projects
• Verified test update in src/lib/stytch.test.ts — test now asserts no credit transaction is created (DB tests cannot run in this environment due to missing pg connection, but the test logic is correct)
• Confirmed no unused imports remain after removing grantCreditForCategory, subDays, and hasReceivedPromotion

Visual Changes

N/A

Reviewer Notes

• The handleSignupPromotion function is kept as a no-op rather than fully deleted because account-verification/page.tsx calls it. Removing the call entirely would also be fine but this approach is more minimal.
• The automatic-welcome-credits category still exists in promoCreditCategories.ts (with amount_usd: 0) because it's referenced by welcomeCredits.ts for checking whether existing users have already received any welcome credits (used in admin tools and customer info).
• The first-topup bonus ($20), survey credits, referral bonuses, and other promo mechanisms are not affected by this change.

Built for Mark by Kilo for Slack

[kilo-code-bot]

WARNING: Zeroing this category amount breaks remaining welcome-credit grants

grantCreditForCategory() falls back to the promo config's amount_usd when callers do not override it. src/scripts/d2025-10-07-backfill-github-welcome.ts:85 still grants automatic-welcome-credits without an explicit amount, so this change will create a $0 transaction while still marking the user as having received welcome credits.

[kilo-code-bot]

Code Review Summary

Status: 1 Issue Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	1
SUGGESTION	0

Issue Details (click to expand)

WARNING

File	Line	Issue
src/lib/promoCreditCategories.ts	175	Setting automatic-welcome-credits to $0 makes remaining grants record a welcome-credit transaction without actually crediting the user.

Other Observations (not in diff)

Issues found in unchanged code that cannot receive inline comments:

File	Line	Issue
src/scripts/d2025-10-07-backfill-github-welcome.ts	86	This script still grants automatic-welcome-credits without overriding amount_usd, so it will now create a $0 transaction.
src/lib/welcomeCredits.ts	16	A zero-dollar automatic-welcome-credits transaction still counts as having received welcome credits, which can incorrectly disqualify the user from follow-up flows.

Fix these issues in Kilo Cloud

Files Reviewed (4 files)

• src/lib/notifications.ts - 0 issues
• src/lib/promoCreditCategories.ts - 1 issue
• src/lib/stytch.test.ts - 0 issues
• src/lib/stytch.ts - 0 issues