Output only satellite - part 2 (#278)

Introduce a new `--output-only` command-line flag and corresponding `ENABLE_OUTPUT_ONLY` environment variable. This allows users to run the assistant in output-only mode, where it only supports announcements. The change includes updates to configuration examples, documentation, and the Docker entrypoint script.

docs/install_application.md

@@ -187,6 +187,7 @@ Environment=PREFERENCES_FILE="/home/pi/linux-voice-assistant/preferences.json"
 # Environment=PROCESSING_SOUND="sounds/processing.wav"
 # Environment=MUTE_SOUND="sounds/mute_switch_on.flac"
 # Environment=UNMUTE_SOUND="sounds/mute_switch_off.flac"
+# Environment=ENABLE_OUTPUT_ONLY="1"
 ExecStart=/home/pi/linux-voice-assistant/docker-entrypoint.sh
 # ExecStart=/home/pi/linux-voice-assistant/docker-entrypoint.sh --additional-parameter-if-you-want
 Restart=always
@@ -265,6 +266,8 @@ The following variables can be configured in the `.env` or in the service file:
 | `PROCESSING_SOUND` | `sounds/processing.wav` | Sound file for processing state |
 | `MUTE_SOUND` | `sounds/mute_switch_on.flac` | Sound file for mute on |
 | `UNMUTE_SOUND` | `sounds/mute_switch_off.flac` | Sound file for Configure Audio Devices
+| `ENABLE_OUTPUT_ONLY` | (optional) | Set to "1" to enable output-only mode |
+
 
 💡 **Note:** For the systemd installation some variables set in the service need to be without `LVA_` prefix.