nook: capture trial email and run the two lifecycle emails

Trials were anonymous — a 14-day trial you cannot talk to. trials gains
an email column (idempotent ALTER), POST /api/the-nook/trial-email
attaches the optional first-launch prompt's answer, and the address
lands in a Brevo list when NOOK_TRIAL_LIST_ID is set. The lifecycle
emails follow: a D+11 trial expiry reminder with a buy link, a purchase
thank-you from the Stripe webhook, and scheduled testimonial (D+3) and
review (D+14) asks via the daily /api/the-nook/lifecycle cron. Rows are
marked before sending so retries never double-send; trial addresses
that already bought get no buy reminder; the endpoint requires a
Bearer secret (CRON_SECRET / NOOK_LIFECYCLE_SECRET) and fails closed
when unconfigured — an open trigger would email real users. All sends
are best-effort and logged, never thrown.

Tests: trial-email (3) and lifecycle (6) suites; full run 539 pass.

Issues: FRE-10, FRE-11

vercel.json

@@ -55,5 +55,8 @@
         }
       ]
     }
+  ],
+  "crons": [
+    { "path": "/api/the-nook/lifecycle", "schedule": "0 13 * * *" }
   ]
 }