#9732 Finish coderouter billing operations and telemetry

Adds hourly Stripe/RDS reconciliation, delayed-event repair, refund and checkout-start analytics, internal runbooks and benchmark tooling, bounded retries/concurrency, privacy-safe Sentry breadcrumbs, and deterministic coverage.

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Summary by cubic

Completes coderouter billing operations and telemetry for the private beta. Adds serialized hourly Stripe↔RDS reconciliation, hardened webhooks (including refunds), privacy‑safe checkout/refund analytics, and lightweight ops tooling.

• New Features

  • Hourly reconciliation cron /api/cron/billing-reconcile (Bearer CRON_SECRET) runs under a global advisory lock to serialize cron/operator runs, uses per-subscription cursor last_reconciled_at, bounded concurrency, and CLI bun coderouter:reconcile-billing with --dry-run; exits nonzero on failures/truncation; returns 503 with Retry-After; scheduled at minute 23 in vercel.json.
  • Webhook always re-fetches the current Stripe subscription; handles charge.refunded by joining invoice→subscription, records analytics, and does not revoke active access.
  • Checkout-start analytics from checkout routes are deferred via Next.js after() with a safe fallback; unified capture adds stable $insert_id, team grouping via $groups, and a single retry on 5xx only.
  • Benchmark harness bun coderouter:benchmark reports status counts, p50/p95/p99, and Server-Timing, and refuses to send route tokens to unapproved origins; runbook docs/coderouter-operations.md covers replay, reconciliation, latency evidence, and observability.

• Bug Fixes

  • Prevents stale Stripe payloads from overwriting newer entitlements; Stripe is authoritative.
  • Stripe catalog provisioning uses /products/search with next_page and curl timeouts/retries; dev stack listens for charge.refunded.
  • Adds privacy-safe Sentry breadcrumb for reconciliation runs; analytics failures never affect billing paths.

Summary by CodeRabbit

• Billing

  • Added automated Stripe subscription reconciliation with drift detection, repair, dry-run support, and failure reporting.
  • Scheduled recurring reconciliation with secure access controls.
  • Improved handling of refunded charges and stale subscription events to keep entitlements accurate.
  • Improved Stripe catalog provisioning and webhook configuration.

• Observability

  • Added checkout-start and refund analytics with retries, deduplication, and privacy-safe event data.

• Operations

  • Added benchmarking and billing-reconciliation command-line tools.
  • Added an operations runbook covering billing recovery, performance checks, and observability practices.