feat(billing): integrate Stripe for subscription management and billing access

- Added billing-related fields to the User model in the database.
- Implemented functions for managing billing access, including trial periods and subscription statuses.
- Created new billing utility functions for Stripe integration.
- Updated onboarding page to include billing overview and workspace creation eligibility.
- Enhanced route access checks to require billing access for certain actions.
- Implemented cleanup scripts for expired billing workspaces and associated media.
- Updated header component to conditionally show app navigation based on billing access.
- Added new migrations for billing-related database changes.

.env.example

@@ -57,6 +57,7 @@ SMTP_FROM="[email protected]"
 # ============================================================================
 # APPLICATION
 # ============================================================================
+NEXT_PUBLIC_APP_URL="http://localhost:3000"
 # development | production | test
 NODE_ENV="development"
 # Disable all app-level rate limiting for local testing. Leave unset to keep rate limiting enabled.
@@ -86,3 +87,11 @@ NEXT_PUBLIC_BUNNY_CDN_URL="your-url-to-bunny-cdn"
 # Bunny orphan cleanup configuration (script + external cron; app runtime does not schedule this)
 # Grace period is fixed at 24 hours in the script.
 # */15 * * * * cd /home/yusuf/Programming/OpenFrame && bun run bunny:cleanup-orphans
+
+# ============================================================================
+# BILLING
+# ============================================================================
+# Stripe recurring price used for paid accounts
+STRIPE_SECRET_KEY="sk_test_..."
+STRIPE_PRICE_ID="prod_UBWFFKZC3d80z4"
+STRIPE_WEBHOOK_SECRET="whsec_..."