feat(13-02): add library filter dropdown and wire all views to respect active filter

- Add selectedLibraryId state + ByLibrary conditional calls to library-store
- Add library filter pass-through methods to library-controller
- Create library-filter dropdown component in top bar
- Wire genre-details, cover-grid, artists-view, genres-view to use ByLibrary queries
- Update album-selection helper to respect library filter
- Regenerate Wails bindings for new ByLibrary methods
- Search remains client-side (automatically filtered by loaded data)
- Playlists remain unfiltered (use separate playlist store)

frontend/index.html

@@ -15,6 +15,7 @@
             <h1 class="title">YellowJacket</h1>
             <h3 class="subtitle">Music how it was meant to bee.</h3>
         </hgroup>
+        <library-filter></library-filter>
         <search-bar></search-bar>
     </header>
     <div class="sidebar">