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)
yonlu
ffc5d9639c