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

src/env/server.ts

@@ -73,7 +73,14 @@ const serverEnvSchema = z.object({
   NOOK_LICENSE_PRIVATE_KEY: z.string().min(1),
   NOOK_STRIPE_SK: z.string().min(1),
   NOOK_STRIPE_WEBHOOK_SECRET: z.string().min(1),
-  NOOK_STRIPE_PRICE_ID: z.string().min(1)
+  NOOK_STRIPE_PRICE_ID: z.string().min(1),
+  // Brevo list the trial-start emails land in (the lifecycle mail's
+  // audience). Optional: capture still stores the address when unset.
+  NOOK_TRIAL_LIST_ID: z.coerce.number().int().positive().optional(),
+  // Bearer secret for the daily lifecycle-email cron. Falls back to
+  // Vercel's CRON_SECRET; unset + no CRON_SECRET = the endpoint denies all.
+  NOOK_LIFECYCLE_SECRET: z.string().min(1).optional(),
+  CRON_SECRET: z.string().min(1).optional()
 });
 
 export type ServerEnv = z.infer<typeof serverEnvSchema>;