Add read-only mode support and enhance logging throughout the application

README.md

@@ -31,6 +31,7 @@ Usage:
 
 Application Options:
       --address=        The IP/DNS and port of the machine that the application is running on. (default: :8080) [$ADDRESS]
+      --read_only       Disable all write operations and run in monitoring-only mode. [$READ_ONLY]
       --data.source=    Set the source of data for the inverter gui. "serial", "tcp" or "mock" (default: serial) [$DATA_SOURCE]
       --data.host=      Host to connect when source is set to tcp. (default: localhost:8139) [$DATA_HOST]
       --data.device=    TTY device to use when source is set to serial. (default: /dev/ttyUSB0) [$DATA_DEVICE]
@@ -54,6 +55,26 @@ Help Options:
   -h, --help            Show this help message
 ```
 
+### Read-Only Mode
+
+Set `READ_ONLY=true` (or `--read_only`) to disable all write operations.
+When read-only mode is enabled, the app still monitors and publishes telemetry, but it will not send commands to the Victron device.
+
+This affects:
+
+- MQTT command handling (`--mqtt.command_topic` commands are ignored)
+- Web UI control actions (`POST /api/remote-panel/state` and `POST /api/remote-panel/standby`)
+
+Example `docker-compose.yml` snippet:
+
+```yaml
+services:
+  invertergui:
+    image: registry.coadcorp.com/nathan/invertergui:latest
+    environment:
+      READ_ONLY: "true"
+```
+
 ## Port 8080
 
 The default HTTP server port is hosted on port 8080. This exposes the HTTP server that hosts the:
@@ -315,6 +336,12 @@ The MQTT client will publish updates to the given broker at the set topic.
 --mqtt.password-file= Path to a file containing the MQTT password [$MQTT_PASSWORD_FILE]
 ```
 
+Related global option:
+
+```bash
+--read_only Disable all write operations and run in monitoring-only mode. [$READ_ONLY]
+```
+
 The MQTT client can be enabled by setting the environment variable `MQTT_ENABLED=true` or flag `--mqtt.enabled`.
 All MQTT configuration can be done via flags or as environment variables.
 The URI for the broker can be configured format should be `scheme://host:port`, where "scheme" is one of "tcp", "ssl", or "ws".