fix: supprimer les variables inutilisées et la fonction morte (warnings Rust)

- metadata.rs: simplifier la query get_missing_books, library_id et
  series_name étaient extraits mais non utilisés
- series.rs: supprimer resolve_series_id jamais appelée

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

apps/api/src/metadata.rs

@@ -515,19 +515,14 @@ pub async fn get_missing_books(
 ) -> Result<Json<MissingBooksDto>, ApiError> {
     // Verify link exists
     let link = sqlx::query(
-        "SELECT eml.library_id, eml.series_id, s.name AS series_name \
-         FROM external_metadata_links eml \
-         JOIN series s ON s.id = eml.series_id \
-         WHERE eml.id = $1",
+        "SELECT eml.series_id FROM external_metadata_links eml WHERE eml.id = $1",
     )
     .bind(id)
     .fetch_optional(&state.pool)
     .await?
     .ok_or_else(|| ApiError::not_found("link not found"))?;
 
-    let library_id: Uuid = link.get("library_id");
     let series_id: Uuid = link.get("series_id");
-    let series_name: String = link.get("series_name");
 
     // Count external books
     let total_external: i64 =

apps/api/src/series.rs

@@ -9,22 +9,6 @@ use crate::{auth::AuthUser, books::BookItem, error::ApiError, state::AppState};
 
 // ─── Helper functions ────────────────────────────────────────────────────────
 
-/// Resolve a series UUID from library_id + name. Returns NotFound if no such series exists.
-pub(crate) async fn resolve_series_id(
-    pool: &sqlx::PgPool,
-    library_id: Uuid,
-    name: &str,
-) -> Result<Uuid, ApiError> {
-    sqlx::query_scalar::<_, Uuid>(
-        "SELECT id FROM series WHERE library_id = $1 AND LOWER(name) = LOWER($2)"
-    )
-    .bind(library_id)
-    .bind(name)
-    .fetch_optional(pool)
-    .await?
-    .ok_or_else(|| ApiError::not_found(format!("series '{}' not found", name)))
-}
-
 /// Get or create a series row, returning its UUID.
 pub(crate) async fn get_or_create_series(
     pool: &sqlx::PgPool,