fix: hide reconnect button when agent is online; add printer encoding/paper_width settings

- WorkstationCard: show RefreshCw reconnect only when agentId set but offline
- DeviceForm: add encoding (utf8/cp866) and paper_width fields for network printers
- Backend: pass device.config in test_device command to agent

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

backend/src/routes/workstations.ts

@@ -322,6 +322,7 @@ const workstationRoutes: FastifyPluginAsync = async (fastify) => {
             dto_user: device.config?.dto_user,
             dto_pass: device.config?.dto_pass,
             dto_device_id: device.config?.dto_device_id,
+            config: device.config,
           },
         }) as { ok: boolean; error?: string; message?: string }
         return result