feat: add per-library download detection auto-schedule

Adds a configurable schedule (manual/hourly/daily/weekly) for the
download detection job in the library settings modal. The indexer
scheduler triggers the job automatically, and the API job poller
processes it — consistent with the reading_status_push pattern.

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

apps/api/src/job_poller.rs

@@ -4,7 +4,7 @@ use sqlx::{PgPool, Row};
 use tracing::{error, info, trace};
 use uuid::Uuid;
 
-use crate::{metadata_batch, metadata_refresh, reading_status_push};
+use crate::{download_detection, metadata_batch, metadata_refresh, reading_status_push};
 
 /// Poll for pending API-only jobs (`metadata_batch`, `metadata_refresh`) and process them.
 /// This mirrors the indexer's worker loop but for job types handled by the API.
@@ -51,6 +51,15 @@ pub async fn run_job_poller(pool: PgPool, interval_seconds: u64) {
                             )
                             .await
                         }
+                        "download_detection" => {
+                            download_detection::process_download_detection(
+                                &pool_clone,
+                                job_id,
+                                library_id,
+                            )
+                            .await
+                            .map(|_| ())
+                        }
                         _ => Err(format!("Unknown API job type: {job_type}")),
                     };
 
@@ -92,6 +101,15 @@ pub async fn run_job_poller(pool: PgPool, interval_seconds: u64) {
                                     },
                                 );
                             }
+                            "download_detection" => {
+                                notifications::notify(
+                                    pool_clone,
+                                    notifications::NotificationEvent::DownloadDetectionFailed {
+                                        library_name,
+                                        error: e.to_string(),
+                                    },
+                                );
+                            }
                             _ => {}
                         }
                     }
@@ -109,7 +127,7 @@ pub async fn run_job_poller(pool: PgPool, interval_seconds: u64) {
     }
 }
 
-const API_JOB_TYPES: &[&str] = &["metadata_batch", "metadata_refresh", "reading_status_push"];
+const API_JOB_TYPES: &[&str] = &["metadata_batch", "metadata_refresh", "reading_status_push", "download_detection"];
 
 async fn claim_next_api_job(pool: &PgPool) -> Result<Option<(Uuid, String, Uuid)>, sqlx::Error> {
     let mut tx = pool.begin().await?;