fix: skip email verification entirely when no mail transport exists

SMTP-less self-hosted instances still marked every account
emailVerified=false and attempted a verification mail that could
never arrive. Now: no transport → accounts are created verified,
the send is skipped, and existing unverified rows are backfilled
on startup. .env.example stops defaulting SMTP_HOST to the
dev-only mailpit service.

Verified live: fresh signup returns emailVerified=true, legacy
unverified users flip on restart, sign-in unaffected.

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Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/auth/src/lib/mail.ts

@@ -30,6 +30,14 @@ async function resolveMailConfig() {
   } as const;
 }
 
+// True when a mail transport exists (Resend key or SMTP host). Verification
+// and reset mails only make sense when mail can actually leave the box.
+export async function hasMailTransport(): Promise<boolean> {
+  const cfg = await resolveMailConfig();
+  if ("resendApiKey" in cfg && cfg.resendApiKey) return true;
+  return "smtp" in cfg && Boolean(cfg.smtp);
+}
+
 export async function sendTransactionalEmail(input: {
   to: string;
   subject: string;