feat(billing): let people try the product before handing over a card

The trial now starts inside the product, at email verification, and Stripe
grants none at all: checkout creates a subscription that bills immediately.
Verifying an address is what buys the seven days, which is also the cheapest
abuse control there is.

An unexpired trial is treated as an entitlement the account already holds, so a
Stripe sync can add access but never retracts a trial that has not run out. That
matters most for the abandoned checkout: the resulting incomplete subscription
carries no trial_end, and writing it through would have erased the days the
account still had and locked it out.

Unpaid accounts are bounded by what they can cost us rather than by what they
can do: one workspace, one project, 3 GiB of direct uploads. YouTube imports,
share links, guests, comments and approvals stay unlimited, because those are
the parts worth trying and they cost nothing. isPaidTier() is the new seam;
hasBillingAccess() answers a different question now that access no longer
implies a card.

Signup CTAs, the pricing card, the comparison pages, the terms and the refund
policy all said the trial converts to a paid plan by itself. It no longer does,
so they say what happens instead. Settings and a banner name both dates that
matter: when the trial ends, and the fifteen days after that during which
nothing is deleted.

/admin/growth compares the two funnels on signup to paid within a fixed 30 day
window, not trial to paid. Dropping the card requirement multiplies trials, so
the old ratio can fall while more people actually pay, and reading it that way
would retire the change for the wrong reason.

app/terms/page.tsx

@@ -58,7 +58,7 @@ export default function TermsOfServicePage() {
               OpenFrame is a video review and approval platform that enables creative professionals
               and their clients to collaborate on video projects through timestamped comments,
               annotations, version management, and approval workflows. The Service is offered on a
-              subscription basis with a free trial period.
+              subscription basis with a free trial period that requires no payment details.
             </p>
           </section>
 
@@ -96,11 +96,12 @@ export default function TermsOfServicePage() {
               5. Subscriptions and Free Trial
             </h2>
             <p>
-              Certain features of the Service require a paid subscription. We offer a{' '}
-              <strong className="text-foreground">7-day free trial</strong> for new accounts, during
-              which you may access paid features at no charge. At the end of the trial period, your
-              subscription will automatically convert to a paid plan unless you cancel before the
-              trial ends.
+              Certain features of the Service require a paid subscription. Every new account
+              receives a <strong className="text-foreground">7-day free trial</strong>, which starts
+              once the account&apos;s email address is verified and requires no credit card. The
+              trial does not convert into a paid plan on its own and nothing is charged while it
+              runs. When it ends, access to paid features stops until you choose to subscribe, and a
+              subscription is billed as soon as you complete checkout.
             </p>
             <p className="mt-3">
               Subscription fees are billed in advance on a monthly or annual basis depending on the