feat(readarr): fetch Readarr disk space and expose it on the CLI

Add ReadarrEvent::GetDiskSpace, mapped to GET /diskspace, and
get_readarr_diskspace, which stores the result on ReadarrData for the
root folder and system views.

Surface it as `managarr readarr list disk-space`, matching the other
three servarrs.

Readarr returns a label field on some records that DiskSpace does not
model; serde drops it, so the CLI prints only the path and the free and
total space, as it does for the other three servarrs.

src/network/readarr_network/system/mod.rs

@@ -1,4 +1,4 @@
-use crate::models::servarr_models::SystemStatus;
+use crate::models::servarr_models::{DiskSpace, SystemStatus};
 use crate::network::readarr_network::ReadarrEvent;
 use crate::network::{Network, RequestMethod};
 use anyhow::Result;
@@ -9,6 +9,23 @@ use log::info;
 mod readarr_system_network_tests;
 
 impl Network<'_, '_> {
+  pub(in crate::network::readarr_network) async fn get_readarr_diskspace(
+    &mut self,
+  ) -> Result<Vec<DiskSpace>> {
+    info!("Fetching Readarr disk space");
+    let event = ReadarrEvent::GetDiskSpace;
+
+    let request_props = self
+      .request_props_from(event, RequestMethod::Get, None::<()>, None, None)
+      .await;
+
+    self
+      .handle_request::<(), Vec<DiskSpace>>(request_props, |disk_space_vec, mut app| {
+        app.data.readarr_data.disk_space_vec = disk_space_vec;
+      })
+      .await
+  }
+
   pub(in crate::network::readarr_network) async fn get_readarr_status(
     &mut self,
   ) -> Result<SystemStatus> {