fix: backend data/ dans %APPDATA%\ObsiGate au lieu de Program Files

- spawn_backend: current_dir → app_data_dir() (writable sur Windows)
- PYTHONPATH = exe_dir pour que 'import backend' trouve le package
- Création de data/ dans app_data_dir avant le spawn

Corrige PermissionError [WinError 5] Access is denied: 'data'

desktop/src/main.rs

@@ -119,8 +119,13 @@ fn spawn_backend(exe_dir: &PathBuf) -> Result<Child, String> {
 
     info!("Starting backend: {}", python.display());
 
+    // Use app data dir as CWD so 'data/' writes go to a writable location (%APPDATA%\ObsiGate)
+    let data_dir = app_data_dir();
+    let _ = fs::create_dir_all(data_dir.join("data"));
+
     let child = Command::new(&python)
-        .current_dir(exe_dir)
+        .current_dir(&data_dir)
+        .env("PYTHONPATH", exe_dir)
         .args([
             "-m", "uvicorn",
             "backend.main:app",