feat: add configurable status mappings for metadata providers

Add a status_mappings table to replace hardcoded provider status
normalization. Users can now configure how provider statuses (e.g.
"releasing", "finie") map to target statuses (e.g. "ongoing", "ended")
via the Settings > Integrations page.

- Migration 0038: status_mappings table with pre-seeded mappings
- Migration 0039: re-normalize existing series_metadata.status values
- API: CRUD endpoints for status mappings, DB-based normalize function
- API: new GET /series/provider-statuses endpoint
- Backoffice: StatusMappingsCard component with create target, assign,
  and delete capabilities
- Fix all clippy warnings across the API crate
- Fix missing OpenAPI schema refs (MetadataStats, ProviderCount)

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

apps/api/src/komga.rs

@@ -154,10 +154,11 @@ pub async fn sync_komga_read_books(
     .fetch_all(&state.pool)
     .await?;
 
+    type BookEntry = (Uuid, String, String);
     // Primary: (series_lower, title_lower) -> Vec<(Uuid, title, series)>
-    let mut primary_map: HashMap<(String, String), Vec<(Uuid, String, String)>> = HashMap::new();
+    let mut primary_map: HashMap<(String, String), Vec<BookEntry>> = HashMap::new();
     // Secondary: title_lower -> Vec<(Uuid, title, series)>
-    let mut secondary_map: HashMap<String, Vec<(Uuid, String, String)>> = HashMap::new();
+    let mut secondary_map: HashMap<String, Vec<BookEntry>> = HashMap::new();
 
     for row in &rows {
         let id: Uuid = row.get("id");