feat(settings): Email (SMTP) BYO card in Settings → Integrations

Replace the SMTP 'coming soon' stub with a real card: host/port/SSL/user/password/
from-address/from-name → crm.settings.smtp.configure, masked status from
crm.settings.smtp.status. Mirrors the Twilio SMS card; demo mode stores hints locally.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/dashboard/dashboard.css

@@ -1253,3 +1253,4 @@
   .dash-root .settings-kv dd { margin: 0; font-size: 13px; font-weight: 600; color: var(--text); font-variant-numeric: tabular-nums; }
   .dash-root .settings-card-actions { display: flex; gap: 8px; align-items: center; margin-top: 2px; }
   .dash-root .settings-card-note { font-size: 12px; color: var(--muted); background: var(--panel-2); border: 1px solid var(--border); border-radius: 10px; padding: 8px 12px; }
+  .dash-root .settings-check { display: inline-flex; align-items: center; gap: 8px; font-size: 13px; color: var(--muted); cursor: pointer; }