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/components/AudioTab/AudioTab.tsx

@@ -23,8 +23,8 @@ import {
 import { apiClient } from '@/lib/api/client';
 import { BOTTOM_SAFE_AREA_PADDING } from '@/lib/constants/ui';
 import { cn } from '@/lib/utils/cn';
-import { usePlayerStore } from '@/stores/playerStore';
 import { usePlatform } from '@/platform/PlatformContext';
+import { usePlayerStore } from '@/stores/playerStore';
 
 interface AudioDevice {
   id: string;
@@ -129,7 +129,7 @@ export function AudioTab() {
     if (await confirm('Delete this channel?')) {
       deleteChannel.mutate(channelId);
     }
-  }
+  };
 
   const allChannels = channels || [];
   const allDevices = devices || [];
@@ -168,7 +168,7 @@ export function AudioTab() {
               </Button>
             </div>
           ) : (
-            <div className="space-y-3 p-2">
+            <div className="space-y-3">
               {allChannels.map((channel) => {
                 const isSelected = selectedChannelId === channel.id;
                 return (
@@ -343,7 +343,9 @@ export function AudioTab() {
             <div className="flex flex-col items-center justify-center py-12 border-2 border-dashed border-muted rounded-md">
               <CheckCircle2 className="h-12 w-12 text-muted-foreground mb-4" />
               <p className="text-muted-foreground text-center">
-                {platform.metadata.isTauri ? 'No audio devices found' : 'Audio device selection requires Tauri'}
+                {platform.metadata.isTauri
+                  ? 'No audio devices found'
+                  : 'Audio device selection requires Tauri'}
               </p>
             </div>
           )}