Upgrade stripe 14 → 22.6.2: pinned API version, v22 type-system migration and constructor/typings changes
The repository pins stripe at ^14.25.0 while the latest release is 22.6.2. The SDK now pins API version 2026-08-26.dahlia, went through a v22 type-system migration, and webhook secrets are now validated as non-empty. The only consumer here is src/billing.ts, so its client construction, typed usage and webhook verification need to be re-checked.
Migration instruction, drafted from the release notes
Upgrade stripe to ^22.6.2 and regenerate the lockfile. Read the installed types before pinning apiVersion; do not guess. Verify every Stripe type still resolves under the v22 type system. Ensure the webhook secret passed to constructEvent cannot be empty, since v22.6.2 now throws. Run the repository's own checks and report.