feat: email integration (nodemailer) + wire into agency/license flows

- src/lib/email.ts: SMTP client with pre-built templates:
  - sendAgencyApprovedEmail (reseller approval + discount)
  - sendAgencyRejectedEmail (reseller rejection + reason)
  - sendLicenseKeyEmail (license key delivery)
  - sendTicketCreatedEmail (ticket confirmation)
- Agency approve route: sends approval email after DB update
- Agency reject route: sends rejection email with reason
- License creation route: sends license key email (fire-and-forget)
- Graceful degradation: if SMTP not configured, logs warning + continues
- nodemailer + @types/nodemailer installed

src/app/api/aos/agency/[id]/reject/route.ts

@@ -60,6 +60,16 @@ export async function PATCH(req: Request, { params }: { params: Promise<{ id: st
       },
     })
 
+    // Send rejection email
+    const { sendAgencyRejectedEmail } = await import('@/lib/email')
+    if (application.company.email) {
+      await sendAgencyRejectedEmail({
+        to: application.company.email,
+        companyName: application.company.name,
+        reason,
+      })
+    }
+
     return NextResponse.json({ ok: true, status: 'rejected', reason })
   } catch (err) {
     const msg = err instanceof Error ? err.message : 'internal server error'