fix(billing): add billing feature flags as Dockerfile build args

NEXT_PUBLIC_ENABLE_PERSONAL_ACCOUNT_BILLING and
NEXT_PUBLIC_ENABLE_TEAM_ACCOUNTS_BILLING must be set at build time
(ARG/ENV in Dockerfile + build args in docker-compose) because Next.js
bakes NEXT_PUBLIC_* into the bundle during 'next build'. Setting them
only as runtime environment vars has no effect.

docker-compose.yml

@@ -333,6 +333,8 @@ services:
         # Stripe (build-time)
         NEXT_PUBLIC_BILLING_PROVIDER: stripe
         NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY: ${NEXT_PUBLIC_STRIPE_PUBLISHABLE_KEY}
+        NEXT_PUBLIC_ENABLE_PERSONAL_ACCOUNT_BILLING: 'true'
+        NEXT_PUBLIC_ENABLE_TEAM_ACCOUNTS_BILLING: 'true'
     restart: unless-stopped
     depends_on:
       supabase-kong: