feat: model management improvements and folder migration

- Add model folder migration with byte-level progress tracking (backend + UI)
- Custom models directory support via VOICEBOX_MODELS_DIR env var passed to sidecar
- Hardcoded model descriptions displayed in model detail cards
- Open model folder button in storage location row
- Remove 'not downloaded' badge from model cards
- Fix server settings scroll offset for audio player
- Fix shell open permission to allow file paths
- Add normalize toggle to generation settings

app/src/lib/hooks/useGenerationForm.ts

@@ -34,6 +34,7 @@ export function useGenerationForm(options: UseGenerationFormOptions = {}) {
   const setIsGenerating = useGenerationStore((state) => state.setIsGenerating);
   const maxChunkChars = useServerStore((state) => state.maxChunkChars);
   const crossfadeMs = useServerStore((state) => state.crossfadeMs);
+  const normalizeAudio = useServerStore((state) => state.normalizeAudio);
   const [downloadingModelName, setDownloadingModelName] = useState<string | null>(null);
   const [downloadingDisplayName, setDownloadingDisplayName] = useState<string | null>(null);
 
@@ -115,6 +116,7 @@ export function useGenerationForm(options: UseGenerationFormOptions = {}) {
         instruct: isQwen ? data.instruct || undefined : undefined,
         max_chunk_chars: maxChunkChars,
         crossfade_ms: crossfadeMs,
+        normalize: normalizeAudio,
       });
 
       toast({