feat(12-02): replace config-page library section with full library management UI

- Add library list with name, path, track count per library
- Add Library button opens folder picker, auto-creates library
- Inline rename with Enter/Escape via overflow menu
- Removal confirmation dialog with real impact counts (tracks, playlists, queue)
- Toast notification with removal summary after library removal
- Add GetAllLibrariesWithTrackCounts + Info type to backend Library struct
- Add Wails binding stubs for AddLibrary, RenameLibrary, RemoveLibrary, GetRemovalImpact
- Add Info, RemovalImpact, RemovalSummary types to models.ts
- Remove old single-directory library config UI (GetLibraryDirectory/SetLibraryDirectory)

frontend/wailsjs/go/library/Library.d.ts

@@ -3,6 +3,8 @@
 import {library} from '../models';
 import {context} from '../models';
 
+export function AddLibrary(arg1:string):Promise<library.Info>;
+
 export function CancelAllScans():Promise<void>;
 
 export function CancelCurrentScan():Promise<void>;
@@ -13,6 +15,8 @@ export function FullRescan():Promise<library.ScanMetrics>;
 
 export function GetAlbumTracks(arg1:number):Promise<Array<library.Track>>;
 
+export function GetAllLibrariesWithTrackCounts():Promise<Array<library.Info>>;
+
 export function GetAlbumsByArtist(arg1:number):Promise<Array<library.Album>>;
 
 export function GetAllAlbums():Promise<Array<library.Album>>;
@@ -23,6 +27,8 @@ export function GetAllGenresWithCounts():Promise<Array<library.GenreWithCount>>;
 
 export function GetAllTracks():Promise<Array<library.Track>>;
 
+export function GetRemovalImpact(arg1:number):Promise<library.RemovalImpact>;
+
 export function GetScanQueueLength():Promise<number>;
 
 export function GetTracksByGenre(arg1:string):Promise<Array<library.Track>>;
@@ -33,6 +39,10 @@ export function IsScanPaused():Promise<boolean>;
 
 export function PauseScan():Promise<void>;
 
+export function RemoveLibrary(arg1:number):Promise<library.RemovalSummary>;
+
+export function RenameLibrary(arg1:number, arg2:string):Promise<void>;
+
 export function QueuedLibraryNames():Promise<Array<string>>;
 
 export function ResumeScan():Promise<void>;