fix(offline_cache): use Queued for reset_track_for_redownload, drop redundant Pending

The previous commit added a Pending variant to OfflineCacheStatus, but
the existing Queued variant already represents 'freshly inserted,
awaiting downloader pickup' (insert_track writes status='queued').
Reusing Queued keeps reset_track_for_redownload semantically aligned
with insert_track and preserves the in-flight count SQL that already
matches WHERE status='downloading' OR status='queued'.

cc

src-tauri/src/offline_cache/db.rs

@@ -381,7 +381,7 @@ impl OfflineCacheDb {
         self.conn()
             .execute(
                 "UPDATE cached_tracks
-                 SET status = 'pending', progress_percent = 0, error_message = NULL
+                 SET status = 'queued', progress_percent = 0, error_message = NULL
                  WHERE track_id = ?1",
                 [track_id as i64],
             )
@@ -743,7 +743,7 @@ mod maintenance_tests {
         db.reset_track_for_redownload(1).unwrap();
 
         let track = db.get_track(1).unwrap().unwrap();
-        assert!(matches!(track.status, OfflineCacheStatus::Pending));
+        assert!(matches!(track.status, OfflineCacheStatus::Queued));
         assert_eq!(track.progress_percent, 0);
         assert!(track.error_message.is_none());
     }

src-tauri/src/offline_cache/mod.rs

@@ -34,7 +34,6 @@ pub use path_validator::{is_offline_root_available, validate_path, PathStatus};
 #[serde(rename_all = "lowercase")]
 pub enum OfflineCacheStatus {
     Queued,
-    Pending,
     Downloading,
     Ready,
     Failed,
@@ -44,7 +43,6 @@ impl OfflineCacheStatus {
     pub fn as_str(&self) -> &'static str {
         match self {
             Self::Queued => "queued",
-            Self::Pending => "pending",
             Self::Downloading => "downloading",
             Self::Ready => "ready",
             Self::Failed => "failed",
@@ -54,7 +52,6 @@ impl OfflineCacheStatus {
     pub fn from_str(s: &str) -> Self {
         match s {
             "queued" => Self::Queued,
-            "pending" => Self::Pending,
             "downloading" => Self::Downloading,
             "ready" => Self::Ready,
             "failed" => Self::Failed,