feat(readarr): test all indexers and expose the command on the CLI

Results come back keyed only by indexer id, so each one is joined
against the cached indexer list to recover a display name, and its
validation failures are flattened into a single line for the results
table.

The endpoint reports failures with a non-2xx status, so the request
ignores the status code and parses the body either way. When the
request itself fails the results table is replaced with an empty one
rather than being left showing the previous run.

src/cli/readarr/mod.rs

@@ -110,6 +110,8 @@ pub enum ReadarrCommand {
     )]
     task_name: ReadarrTaskName,
   },
+  #[command(about = "Test all Readarr indexers")]
+  TestAllIndexers,
   #[command(
     about = "Test the indexer with the given ID. Note that a successful test returns an empty JSON body; i.e. '{}'"
   )]
@@ -247,6 +249,14 @@ impl<'a, 'b> CliCommandHandler<'a, 'b, ReadarrCommand> for ReadarrCliHandler<'a,
           .await?;
         serde_json::to_string_pretty(&resp)?
       }
+      ReadarrCommand::TestAllIndexers => {
+        println!("Testing all Readarr indexers. This may take a minute...");
+        let resp = self
+          .network
+          .handle_network_event(ReadarrEvent::TestAllIndexers.into())
+          .await?;
+        serde_json::to_string_pretty(&resp)?
+      }
       ReadarrCommand::TestIndexer { indexer_id } => {
         let resp = self
           .network