fix(analysis): native library backfill coordinator for advanced strategy (#881)

* feat(analysis): native library backfill coordinator for advanced strategy

Move advanced analytics scheduling from the webview loop into a Rust
background worker (configure + spawn_blocking batch/enqueue), matching
cover backfill. Scan hash+BPM gap tracks instead of the full library;
suppress low-priority analysis UI events; limit loudness refresh IPC to
the playback window.

* fix(analysis): flat backfill configure IPC and restore probe track-perf

Use flattened Tauri args like cover backfill so release/prod invoke works;
keep emitting analysis:track-perf for library low-priority work so Performance
Probe tpm/last-track stats update while waveform/enrichment UI events stay suppressed.

* chore(analysis): fix clippy and drop duplicate TS backfill policy

Allow too_many_arguments on library_analysis_backfill_configure for CI;
remove unused frontend batch API and TS watermark helpers now owned in Rust;
clarify analysis_emits_ui_events comment for low-priority track-perf.

* docs: CHANGELOG and credits for PR #881 native analysis backfill

src-tauri/src/library_analysis_backfill/mod.rs

@@ -0,0 +1,59 @@
+//! Library analysis backfill — native coordinator (advanced analytics strategy).
+
+mod worker;
+
+use std::sync::Arc;
+
+use tauri::{AppHandle, Manager};
+use worker::{
+    spawn_coordinator, setup_library_sync_idle_listener, LibraryAnalysisBackfillSession,
+    LibraryAnalysisBackfillWorker,
+};
+
+
+pub fn init_library_analysis_backfill(app: &AppHandle) -> Result<(), String> {
+    let worker = Arc::new(LibraryAnalysisBackfillWorker::new());
+    app.manage(worker.clone());
+    setup_library_sync_idle_listener(app);
+    spawn_coordinator(app, worker);
+    Ok(())
+}
+
+#[tauri::command]
+#[allow(clippy::too_many_arguments)] // Tauri command surface — args map 1:1 to the JS call (like cover configure + workers).
+pub async fn library_analysis_backfill_configure(
+    app: AppHandle,
+    enabled: bool,
+    server_index_key: String,
+    library_server_id: String,
+    server_url: String,
+    username: String,
+    password: String,
+    workers: u32,
+) -> Result<(), String> {
+    let worker = app
+        .try_state::<Arc<LibraryAnalysisBackfillWorker>>()
+        .ok_or_else(|| "library analysis backfill worker not initialized".to_string())?;
+
+    let session = if enabled
+        && !server_index_key.is_empty()
+        && !library_server_id.is_empty()
+        && !server_url.is_empty()
+    {
+        Some(LibraryAnalysisBackfillSession {
+            server_index_key,
+            library_server_id,
+            server_url,
+            username,
+            password,
+            workers: workers.max(1),
+        })
+    } else {
+        None
+    };
+
+    worker
+        .set_session(enabled && session.is_some(), session)
+        .await;
+    Ok(())
+}