Add Jellyfin library mapping support

Add support for Jellyfin library-to-category mappings used during import. Key changes:

- UI: ImporterView now lets users fetch Jellyfin libraries, configure per-library category (TV/Anime/Movies/Music/skip) and optional path segments, and persists mappings to API settings and localStorage.
- API/types: Add jellyfin_library_mappings to ApiSettingsItem/CreateSettingsInput and UserSettings (JSON string of LibraryMapping[]), and wire conversion helpers in src/api.ts and src/types.ts.
- Jellyfin importer: Introduce LibraryMapping type, fetchJellyfinLibraries, helper functions to resolve library from ParentId or Path (extractLibraryFromPath, findLibraryForItem), and update item conversion (movies/series/albums) to apply mappings and skip items marked 'skip'. Import flow now fetches libraries to build id->name map and passes mappings through to converters.

This enables category-aware imports and allows skipping libraries during Jellyfin imports.

src/types.ts

@@ -118,6 +118,7 @@ export interface UserSettings {
   autoPlayTrailers: boolean;
   language: string;
   theme: 'light' | 'dark' | 'system';
+  jellyfinLibraryMappings?: string; // JSON string of LibraryMapping[]
   createdAt?: string;
   updatedAt?: string;
 }