aisman

Session 144, Step 40: Fix affiliate ledger not created when using discount code on pro subscription
- AIM-2752 Fix affiliate ledger not created when using discount code on pro subscription
- AIM-2755 Auto-create first project user story with guided instructions on project creation
- AIM-2756 Show discount code field in checkout pane for first-time discount users
- AIM-2757 Fix 'Could not load pricing' error and prevent upgrade without known price
- AIM-2758 Disable editable Quantity field in Paddle checkout for individual subscriptions

Outcome:
### Summary

Implemented first-project onboarding (auto story + guided instructions), gated the checkout discount-code section on first-time use, fixed the upgrade pricing failure so the user can never proceed without a known price, and added a server-side safety net for personal-subscription quantity overcharge (detect > 1, refund the excess via a new Paddle adjustment API call, notify the user by email).

Fixed the affiliate ledger bug: the reward is no longer passed through (or read back from) Paddle. The discount code stays internal in `Payment.PayDescr`, and a shared `AffiliateRewardService` records the earning from both the Paddle webhook and the client-side `apply-transaction` path.

JavaScript syntax checks pass and the full C# build succeeds (`Build succeeded`) with no code errors.