feat(qt): merge media-server rows into both local search paths

`media_servers_qt::search_tracks` was written with the rest of the stack
and never called — the compiler's dead-code warning was the only thing
that said so. Both places that merge Plex now merge the media servers
too: the Local Library Tracks tab and the cortinilla's local section.

Two asymmetries are deliberate:

- Page 0 only, in the Tracks tab, for the same reason the Plex arm is
  page 0 only: these caches are bounded sets read whole, so re-merging
  them per page would repeat every remote row once per local page.
- BOUNDED in the cortinilla, unlike the Plex arm. The Plex cache is read
  whole because it always was; a media-server mirror can hold 50k rows
  and that path runs on every keystroke, so it takes the same limit the
  caller asked the local query for.

Verified on the bench: "totsugeki" in the Tracks tab returns Jellyfin
rows first, then the Plex ones.

cc

crates/qbz-qt/src/local_albums.rs

@@ -305,8 +305,17 @@ pub fn load_tracks_page_blocking(reset: bool) -> Result<(Vec<TrackRow>, bool), S
     // make pagination over-report.
     let has_more = page.len() as u64 == TRACKS_PAGE;
 
-    if crate::local_plex::is_enabled() && offset == 0 {
-        let mut merged = crate::local_plex::search_tracks(&query);
+    if offset == 0 {
+        // Plex AND the media servers, in one merge. Page 0 only, for the same
+        // reason the Plex arm was page 0 only: these caches are bounded sets
+        // read whole, so re-merging them on every page would repeat every
+        // remote row once per page of local results.
+        let mut merged = if crate::local_plex::is_enabled() {
+            crate::local_plex::search_tracks(&query)
+        } else {
+            Vec::new()
+        };
+        merged.extend(crate::media_servers_qt::search_tracks(&query, None));
         if !merged.is_empty() {
             merged.append(&mut page);
             if sort != "default" {

crates/qbz-qt/src/search_local.rs

@@ -426,12 +426,21 @@ pub(crate) async fn load_cortinilla_local(
             db.search_with_filter_page(q.trim(), 0, limit, true, exclude_network, "default")
         })
         .unwrap_or_default();
-        if plex_enabled {
-            // PREPEND so Plex content is visible without scrolling past a full
-            // local page. See the module header: this can starve the local-file
-            // tracks out of the track section, and that is the reference's
-            // behaviour, reproduced.
-            let mut merged = crate::local_plex::search_tracks(q.trim());
+        // PREPEND so remote content is visible without scrolling past a full
+        // local page. See the module header: this can starve the local-file
+        // tracks out of the track section, and that is the reference's
+        // behaviour, reproduced — now for every remote source, not just Plex.
+        let mut merged = if plex_enabled {
+            crate::local_plex::search_tracks(q.trim())
+        } else {
+            Vec::new()
+        };
+        // BOUNDED, unlike the Plex arm. The Plex cache is read whole because
+        // it always was; a media-server mirror can hold 50k rows and this runs
+        // on every keystroke of the cortinilla, so it takes the same limit the
+        // caller asked the local query for.
+        merged.extend(crate::media_servers_qt::search_tracks(q.trim(), Some(limit as u32)));
+        if !merged.is_empty() {
             merged.append(&mut rows);
             rows = merged;
         }