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

tauri/src-tauri/src/main.rs

@@ -16,6 +16,7 @@ struct ServerState {
     child: Mutex<Option<tauri_plugin_shell::process::CommandChild>>,
     server_pid: Mutex<Option<u32>>,
     keep_running_on_close: Mutex<bool>,
+    models_dir: Mutex<Option<String>>,
 }
 
 #[command]
@@ -23,7 +24,16 @@ async fn start_server(
     app: tauri::AppHandle,
     state: State<'_, ServerState>,
     remote: Option<bool>,
+    models_dir: Option<String>,
 ) -> Result<String, String> {
+    // Store models_dir for use on restart (empty string means reset to default)
+    if let Some(ref dir) = models_dir {
+        if dir.is_empty() {
+            *state.models_dir.lock().unwrap() = None;
+        } else {
+            *state.models_dir.lock().unwrap() = Some(dir.clone());
+        }
+    }
     // Check if server is already running (managed by this app instance)
     if state.child.lock().unwrap().is_some() {
         return Ok(format!("http://127.0.0.1:{}", SERVER_PORT));
@@ -274,6 +284,12 @@ async fn start_server(
     let port_str = SERVER_PORT.to_string();
     let is_remote = remote.unwrap_or(false);
 
+    // Resolve the custom models directory from the parameter or stored state
+    let effective_models_dir = models_dir.or_else(|| state.models_dir.lock().unwrap().clone());
+    if let Some(ref dir) = effective_models_dir {
+        println!("Custom models directory: {}", dir);
+    }
+
     // If CUDA binary exists, launch it directly instead of the bundled sidecar
     let spawn_result = if let Some(ref cuda_path) = cuda_binary {
         println!("Launching CUDA backend: {:?}", cuda_path);
@@ -282,6 +298,9 @@ async fn start_server(
         if is_remote {
             cmd = cmd.args(["--host", "0.0.0.0"]);
         }
+        if let Some(ref dir) = effective_models_dir {
+            cmd = cmd.env("VOICEBOX_MODELS_DIR", dir);
+        }
         cmd.spawn()
     } else {
         // Use the bundled CPU sidecar
@@ -289,6 +308,9 @@ async fn start_server(
         if is_remote {
             sidecar = sidecar.args(["--host", "0.0.0.0"]);
         }
+        if let Some(ref dir) = effective_models_dir {
+            sidecar = sidecar.env("VOICEBOX_MODELS_DIR", dir);
+        }
         println!("Spawning server process...");
         sidecar.spawn()
     };
@@ -613,9 +635,19 @@ async fn stop_server(state: State<'_, ServerState>) -> Result<(), String> {
 async fn restart_server(
     app: tauri::AppHandle,
     state: State<'_, ServerState>,
+    models_dir: Option<String>,
 ) -> Result<String, String> {
     println!("restart_server: stopping current server...");
 
+    // Update stored models_dir: empty string means reset to default, non-empty means set
+    if let Some(ref dir) = models_dir {
+        if dir.is_empty() {
+            *state.models_dir.lock().unwrap() = None;
+        } else {
+            *state.models_dir.lock().unwrap() = Some(dir.clone());
+        }
+    }
+
     // Stop the current server
     stop_server(state.clone()).await?;
 
@@ -623,9 +655,9 @@ async fn restart_server(
     println!("restart_server: waiting for port release...");
     tokio::time::sleep(tokio::time::Duration::from_millis(1000)).await;
 
-    // Start server again (will auto-detect CUDA binary)
+    // Start server again (will auto-detect CUDA binary and use stored models_dir)
     println!("restart_server: starting server...");
-    start_server(app, state, None).await
+    start_server(app, state, None, None).await
 }
 
 #[command]
@@ -686,6 +718,7 @@ pub fn run() {
             child: Mutex::new(None),
             server_pid: Mutex::new(None),
             keep_running_on_close: Mutex::new(false),
+            models_dir: Mutex::new(None),
         })
         .manage(audio_capture::AudioCaptureState::new())
         .manage(audio_output::AudioOutputState::new())