fix: Remove unused app_size variable (cppcheck)

get-started/csi_recv_router/main/app_main.c

@@ -1532,14 +1532,6 @@ static int cmd_handle(const char *cmd, char *reply, size_t reply_size)
         /* Partition info */
         const esp_partition_t *running = esp_ota_get_running_partition();
         uint32_t part_size = running ? running->size : 0;
-        uint32_t app_size = 0;
-        if (running) {
-            esp_app_desc_t desc;
-            if (esp_ota_get_partition_description(running, &desc) == ESP_OK) {
-                /* App size not directly available, use partition size */
-                app_size = part_size;
-            }
-        }
 
         snprintf(reply, reply_size,
                  "OK STATUS uptime=%s uptime_s=%lld heap=%lu rssi=%d channel=%d tx_power=%d rate=%d csi_rate=%d"