Update billing progress and portal/API testing context

OPEN_THREADS.md

@@ -100,9 +100,14 @@ Completed:
 - console routing corrected
 - control plane switched to IP-based service communication
 - Velocity rehydration uses DB + Redis instead of Proxmox live state
+- billing foundation added to Prisma/User model (`stripeCustomerId`, `subscriptionStatus`, `plan`)
+- migration history drift reconciled cleanly without DB reset
+- Stripe sandbox checkout flow now reaches Stripe successfully for a normal test user
+- Stripe customer ID persistence works
 
 Outstanding:
-- Billing / Stripe integration
+- Stripe webhook delivery/reachability for non-public API path
+- webhook-driven persistence of `subscriptionStatus` and `plan`
 - password reset flow verification
 - usage limits / quota enforcement
 - simplify and harden host-native `devProxy`
@@ -121,12 +126,14 @@ Completed:
 - dev file browser support
 - site copy rewrite
 - pricing page updated
+- billing page/auth compatibility work started for API v2 billing state
 
 Outstanding:
 - confirm "Open IDE" button fully uses hosted URL flow
 - SSH config snippet for power users
 - user onboarding flow
 - email notifications
+- finish portal billing page alignment with API v2 (`/api/billing`, checkout redirect, billing-exempt/admin handling, trialing/active states)
 - dashboard information architecture refresh — remove or rethink duplicate resource overview/cards
 - implement "spotlight server" carousel on dashboard (rotating single server card with status/players, click-through to console)
 - remove `testdaemon` binary from repo root
@@ -164,7 +171,7 @@ Optional / Nonessential:
 ## Pre-Launch Checklist
 
 Outstanding before launch:
-- Billing / Stripe integration
+- Billing / Stripe integration (webhook delivery + state persistence still pending)
 - game server world backup / restore
 - user onboarding flow
 - password reset flow verification