- New _payment_js.html: conditionally loads Paddle.js or nothing (Stripe
uses server-side Checkout Session). Provides startCheckout() helper.
- All checkout templates use _payment_js.html instead of _paddle.html
- export.html, signup_step_4.html: Paddle.Checkout.open() → startCheckout()
- dashboard_boosts.html: inline onclick → buyItem() with server round-trip
- New /billing/checkout/item endpoint for single-item purchases (boosts, credits)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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