refactor: share one DownloadStatus enum across the servarr models

DownloadStatus was declared four times, byte for byte identically, in
radarr_models, sonarr_models, lidarr_models, and readarr_models: the same
variants, the same derive list, and the same serde, strum, and display_style
attributes. Every servarr's queue endpoint reports the same status
vocabulary, so there is nothing servarr specific about the type.

Move it into servarr_models, preserving that file's alphabetical ordering
(between DiskSpace and IndexerSettings), and drop the four copies. The
DownloadRecord types keep their per-servarr shapes and now reference the
shared enum.

The two enum tests, test_download_status_display and
test_download_status_to_display_str, were likewise duplicated in the four
per-servarr model test files. Keep one copy of each in servarr_models_tests
alongside the other shared enum display tests and delete the rest. The
per-servarr DownloadRecord fallback deserialization tests stay where they
are since they exercise each servarr's own record type.

Behavior is unchanged. Every remaining edit is an import path update.

src/models/readarr_models_tests.rs

@@ -7,14 +7,14 @@ mod tests {
 
   use crate::models::readarr_models::{
     AddAuthorSearchResult, BlocklistItem, BlocklistResponse, Book, BookFile, DownloadRecord,
-    DownloadStatus, DownloadsResponse, Edition, MediaInfo, MonitorType, NewItemMonitorType,
+    DownloadsResponse, Edition, MediaInfo, MonitorType, NewItemMonitorType,
     ReadarrHistoryEventType, ReadarrHistoryItem, ReadarrHistoryWrapper, ReadarrRelease,
     ReadarrTask, ReadarrTaskName,
   };
   use crate::models::servarr_models::{
-    DiskSpace, HostConfig, Indexer, IndexerSettings, IndexerTestResult, Log, LogResponse,
-    MetadataProfile, QualityProfile, QueueEvent, RootFolder, SecurityConfig, SystemStatus, Tag,
-    Update,
+    DiskSpace, DownloadStatus, HostConfig, Indexer, IndexerSettings, IndexerTestResult, Log,
+    LogResponse, MetadataProfile, QualityProfile, QueueEvent, RootFolder, SecurityConfig,
+    SystemStatus, Tag, Update,
   };
   use crate::models::{
     Serdeable,
@@ -644,40 +644,6 @@ mod tests {
     assert_str_eq!(AuthorStatus::Deleted.to_display_str(), "Deleted");
   }
 
-  #[test]
-  fn test_download_status_display() {
-    assert_str_eq!(DownloadStatus::Unknown.to_string(), "unknown");
-    assert_str_eq!(DownloadStatus::Queued.to_string(), "queued");
-    assert_str_eq!(DownloadStatus::Paused.to_string(), "paused");
-    assert_str_eq!(DownloadStatus::Downloading.to_string(), "downloading");
-    assert_str_eq!(DownloadStatus::Completed.to_string(), "completed");
-    assert_str_eq!(DownloadStatus::Failed.to_string(), "failed");
-    assert_str_eq!(DownloadStatus::Warning.to_string(), "warning");
-    assert_str_eq!(DownloadStatus::Delay.to_string(), "delay");
-    assert_str_eq!(
-      DownloadStatus::DownloadClientUnavailable.to_string(),
-      "downloadClientUnavailable"
-    );
-    assert_str_eq!(DownloadStatus::Fallback.to_string(), "fallback");
-  }
-
-  #[test]
-  fn test_download_status_to_display_str() {
-    assert_str_eq!(DownloadStatus::Unknown.to_display_str(), "Unknown");
-    assert_str_eq!(DownloadStatus::Queued.to_display_str(), "Queued");
-    assert_str_eq!(DownloadStatus::Paused.to_display_str(), "Paused");
-    assert_str_eq!(DownloadStatus::Downloading.to_display_str(), "Downloading");
-    assert_str_eq!(DownloadStatus::Completed.to_display_str(), "Completed");
-    assert_str_eq!(DownloadStatus::Failed.to_display_str(), "Failed");
-    assert_str_eq!(DownloadStatus::Warning.to_display_str(), "Warning");
-    assert_str_eq!(DownloadStatus::Delay.to_display_str(), "Delay");
-    assert_str_eq!(
-      DownloadStatus::DownloadClientUnavailable.to_display_str(),
-      "Download Client Unavailable"
-    );
-    assert_str_eq!(DownloadStatus::Fallback.to_display_str(), "Fallback");
-  }
-
   #[test]
   fn test_readarr_history_event_type_display() {
     assert_str_eq!(ReadarrHistoryEventType::Unknown.to_string(), "unknown");