perf(indexer): éliminer le pre-count WalkDir en mode incrémental + concurrence adaptative

- Incremental rebuild: remplace le WalkDir de comptage par un COUNT(*) SQL
  → incrémental 67s → 25s (-62%) sur disque externe
- Full rebuild: conserve le WalkDir (DB vidée avant le comptage)
- Concurrence par défaut: num_cpus/2 clampé [2,8] au lieu de 2 fixe
- Ajoute num_cpus comme dépendance workspace
- Backoffice jobs: un seul formulaire avec formAction par bouton (icônes rétablies)
- infra/perf.sh: corrige l'endpoint /index/jobs/:id (pas /details), exporte BASE_API/TOKEN

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/indexer/Cargo.toml

@@ -13,6 +13,7 @@ chrono.workspace = true
 futures = "0.3"
 image.workspace = true
 notify = "6.1"
+num_cpus.workspace = true
 parsers = { path = "../../crates/parsers" }
 rand.workspace = true
 rayon.workspace = true

apps/indexer/src/analyzer.rs

@@ -67,7 +67,10 @@ async fn load_thumbnail_config(pool: &sqlx::PgPool) -> ThumbnailConfig {
 }
 
 async fn load_thumbnail_concurrency(pool: &sqlx::PgPool) -> usize {
-    let default_concurrency = 2;
+    // Default: half the logical CPUs, clamped between 2 and 8.
+    // Archive extraction is I/O bound but benefits from moderate parallelism.
+    let cpus = num_cpus::get();
+    let default_concurrency = (cpus / 2).clamp(2, 8);
     let row = sqlx::query(r#"SELECT value FROM app_settings WHERE key = 'limits'"#)
         .fetch_optional(pool)
         .await;

apps/indexer/src/job.rs

@@ -238,27 +238,42 @@ pub async fn process_job(
             .await?
     };
 
-    // Count total files for progress estimation
-    let library_paths: Vec<String> = libraries
-        .iter()
-        .map(|library| {
-            crate::utils::remap_libraries_path(&library.get::<String, _>("root_path"))
-        })
-        .collect();
+    // Count total files for progress estimation.
+    // For incremental rebuilds, use the DB count (instant) — the filesystem will be walked
+    // once during discovery anyway, no need for a second full WalkDir pass.
+    // For full rebuilds, the DB is already cleared, so we must walk the filesystem.
+    let library_ids: Vec<uuid::Uuid> = libraries.iter().map(|r| r.get("id")).collect();
 
-    let total_files: usize = library_paths
-        .par_iter()
-        .map(|root_path| {
-            walkdir::WalkDir::new(root_path)
-                .into_iter()
-                .filter_map(Result::ok)
-                .filter(|entry| {
-                    entry.file_type().is_file()
-                        && parsers::detect_format(entry.path()).is_some()
-                })
-                .count()
-        })
-        .sum();
+    let total_files: usize = if !is_full_rebuild {
+        let count: i64 = sqlx::query_scalar(
+            "SELECT COUNT(*) FROM book_files bf JOIN books b ON b.id = bf.book_id WHERE b.library_id = ANY($1)"
+        )
+        .bind(&library_ids)
+        .fetch_one(&state.pool)
+        .await
+        .unwrap_or(0);
+        count as usize
+    } else {
+        let library_paths: Vec<String> = libraries
+            .iter()
+            .map(|library| {
+                crate::utils::remap_libraries_path(&library.get::<String, _>("root_path"))
+            })
+            .collect();
+        library_paths
+            .par_iter()
+            .map(|root_path| {
+                walkdir::WalkDir::new(root_path)
+                    .into_iter()
+                    .filter_map(Result::ok)
+                    .filter(|entry| {
+                        entry.file_type().is_file()
+                            && parsers::detect_format(entry.path()).is_some()
+                    })
+                    .count()
+            })
+            .sum()
+    };
 
     info!(
         "[JOB] Found {} libraries, {} total files to index",