feat(billing): paywall conversion pass (deferred first charge, trial touchpoint, sell-view upgrade) (#991)

* feat(billing): paywall conversion pass: deferred first charge, trial touchpoint, sell-view upgrade

- checkout passes subscription_data.trial_end (trial grant expiry, 49h floor)
  so a mid-trial upgrade costs 0 kr today instead of double-billing days the
  company already has free; billing/status counts 'trialing' as paying
- trial countdown pill in the sidebar (CompanyContext.trialEndsAt via
  getCompanyEntitlements); hidden for sandbox, dev bypass, and once any
  non-trial grant is active
- sell view: what-happens-when timeline, free-vs-paid comparison table,
  risk-reversal copy + chevron CTA, post-checkout confirmation state

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(billing): review triage: fail-closed trial lookup, hourly countdown refresh, BFL retention note

- checkout returns 500 (no Stripe session) when the trial-grant lookup errors,
  instead of silently charging immediately after the UI promised 0 kr idag
- sidebar trial countdown recomputes hourly so a long-lived tab stays honest
- sell-view retention copy states BFL 7-year retention explicitly
  (compliance-bot suggestion)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* chore: retrigger CI (pull_request event delivery stuck)

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

contexts/CompanyContext.tsx

@@ -13,6 +13,12 @@ interface CompanyContextValue {
   isSandbox: boolean
   /** PAID capability keys the active company currently holds (entitled + enabled). */
   capabilities: CapabilityKey[]
+  /**
+   * Trial expiry while the trial is the company's only source of paid access;
+   * null when paying/comped or after the trial lapsed. Drives the countdown
+   * touchpoint in the sidebar.
+   */
+  trialEndsAt: string | null
 }
 
 const CompanyContext = createContext<CompanyContextValue | null>(null)