feat(admin): per-port email/Documenso/branding/reminder settings + invitations

Centralizes everything operators need to configure into the admin panel,
each setting per-port with env fallback.

New admin pages
- /admin              landing page linking to every admin section as a card
- /admin/email        FROM name+address, reply-to, signature/footer HTML,
                      optional SMTP host/port/user/pass override
- /admin/documenso    API URL+key override, EOI Documenso template ID,
                      default EOI pathway (documenso-template vs inapp),
                      "Test connection" button
- /admin/branding     logo URL, primary color, app name, email
                      header/footer HTML
- /admin/reminders    port-level defaults for new interests +
                      port-wide daily-digest delivery window
- /admin/invitations  send / list / resend / revoke CRM invitations

Per-user reminder digest
- /notifications/preferences gains a Reminder digest card:
  immediate / daily / weekly / off, with HH:MM, day-of-week,
  IANA timezone fields. Stored in user_profiles.preferences.reminders.

Plumbing
- port-config.ts typed accessors (getPortEmailConfig, getPortDocumensoConfig,
  getPortBrandingConfig, getPortReminderConfig) — settings → env fallback.
- sendEmail accepts optional portId; resolves From/SMTP from settings
  when supplied.
- documensoFetch + downloadSignedPdf accept optional portId; each public
  function takes it through. checkDocumensoHealth() backs the test button.
- crm-invite.service gains listCrmInvites / revokeCrmInvite / resendCrmInvite
  with audit-log entries (revoke_invite, resend_invite added to AuditAction).
- AdminLandingPage card grid + shared SettingsFormCard component to remove
  per-page form boilerplate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/app/(dashboard)/[portSlug]/admin/invitations/page.tsx

@@ -0,0 +1,16 @@
+import { InvitationsManager } from '@/components/admin/invitations/invitations-manager';
+
+export default function InvitationsPage() {
+  return (
+    <div className="space-y-6">
+      <div>
+        <h1 className="text-2xl font-semibold">Invitations</h1>
+        <p className="text-sm text-muted-foreground">
+          Send a single-use invitation to a new CRM user. The recipient sets their own password via
+          the link in the email.
+        </p>
+      </div>
+      <InvitationsManager />
+    </div>
+  );
+}