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/metadata_providers/open_library.rs

@@ -144,10 +144,10 @@ async fn search_series_impl(
                 entry.publishers.push(p.clone());
             }
         }
-        if entry.start_year.is_none() || first_publish_year.map_or(false, |y| entry.start_year.unwrap() > y) {
-            if first_publish_year.is_some() {
-                entry.start_year = first_publish_year;
-            }
+        if (entry.start_year.is_none() || first_publish_year.is_some_and(|y| entry.start_year.unwrap() > y))
+            && first_publish_year.is_some()
+        {
+            entry.start_year = first_publish_year;
         }
         if entry.cover_url.is_none() {
             entry.cover_url = cover_url;