fix: clarify config setup — manual entry from toml, not file import

docs/gui-quickstart-linux.md

@@ -24,7 +24,7 @@ No installation required. The AppImage is self-contained.
 
 Your server administrator will provide either a `client.toml` config file or a QR code image.
 
-- **TOML file:** tap **Import from file** and select the `.toml` file.
+- **TOML config:** your administrator will provide a `client.toml` file. Open it in a text editor and enter the server address, port, and key values into the corresponding fields in the app.
 - **QR code:** tap **Scan QR code** and point the camera at the QR code image, or use **Import QR image** to select an image file from disk.
 
 ## 5. Privileges