fix(portable): harden persistence and release paths (#15)

Preserve legacy source data when portable sanitization cannot replace it, reject malformed settings without panicking, and make portable pairing regeneration durable before UI state changes.\n\nMake the packaged smoke assertion tolerate slow WebView startup and clarify AppImage storage behavior.\n\nRefs #15

src-tauri/src/lib.rs

@@ -4350,6 +4350,7 @@ fn get_free_space(app_handle: tauri::AppHandle, path: String) -> Result<String,
 
 #[tauri::command]
 fn set_keychain_password(
+    database: tauri::State<'_, crate::db::DbState>,
     state: tauri::State<'_, AppState>,
     id: String,
     password: String,
@@ -4357,6 +4358,8 @@ fn set_keychain_password(
     if state.storage_layout.is_portable()
         && id == crate::db::PAIRING_TOKEN_KEYCHAIN_ID
     {
+        let connection = database.lock()?;
+        crate::db::save_pairing_token_to_settings(&connection, &password, true)?;
         return Ok(());
     }
     crate::db::set_keychain_password(&id, &password)