feat(08-02): add snapshot download button to config history timeline

- Add SnapshotResponse interface and getSnapshot API method
- Add deviceName prop to ConfigHistorySection
- Add download handler that fetches snapshot and triggers .rsc file download
- Add Download icon button on each timeline entry with stopPropagation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/routes/_authenticated/tenants/$tenantId/devices/$deviceId.tsx

@@ -649,7 +649,7 @@ function DeviceDetailPage() {
             </div>
 
             {/* Configuration History */}
-            <ConfigHistorySection tenantId={tenantId} deviceId={deviceId} />
+            <ConfigHistorySection tenantId={tenantId} deviceId={deviceId} deviceName={device.hostname} />
           </>
         }
         alertsContent={