Fix paho-mqtt v2.x compatibility

Handle both paho-mqtt v1.x and v2.x in MQTTPublisher:
- Try v2.x format with callback_api_version first
- Fall back to v1.x format if needed
- Ensures compatibility across different paho-mqtt versions

Fixes: ValueError when using paho-mqtt 2.0+

SETUP_ON_PI.md

@@ -34,7 +34,7 @@ source .venv/bin/activate
 ### 4. Install Python Dependencies
 ```bash
 pip install --upgrade pip
-pip install bluepy paho-mqtt
+pip install pybluez bluepy paho-mqtt
 
 # Or install the package in development mode
 pip install -e .
@@ -43,8 +43,12 @@ pip install -e .
 ### 5. Set Bluetooth Capabilities
 This allows Python to access Bluetooth without sudo:
 ```bash
-# Set capabilities on the Python interpreter in the venv
-sudo setcap 'cap_net_raw,cap_net_admin+eip' .venv/bin/python3
+# Set capabilities on the actual Python binary (not the symlink)
+sudo setcap 'cap_net_raw,cap_net_admin+eip' $(readlink -f .venv/bin/python3)
+
+# Verify it was set correctly
+getcap $(readlink -f .venv/bin/python3)
+# Should show: cap_net_raw,cap_net_admin+eip
 ```
 
 ### 6. Configure the Application
@@ -88,13 +92,13 @@ Press Ctrl+C to stop.
 If you get permission errors:
 ```bash
 # Check if capabilities are set
-getcap .venv/bin/python3
+getcap $(readlink -f .venv/bin/python3)
 
 # If not set, run:
-sudo setcap 'cap_net_raw,cap_net_admin+eip' .venv/bin/python3
+sudo setcap 'cap_net_raw,cap_net_admin+eip' $(readlink -f .venv/bin/python3)
 
 # Verify Bluetooth device is up
-hciconfig hci0 up
+sudo hciconfig hci0 up
 ```
 
 ### MQTT Connection Issues

src/sensorpajen/mqtt_publisher.py

@@ -23,7 +23,16 @@ class MQTTPublisher:
     
     def _setup_client(self):
         """Setup MQTT client with callbacks."""
-        self.client = mqtt.Client(config.MQTT_CLIENT_ID)
+        # Handle both paho-mqtt v1.x and v2.x
+        try:
+            # Try v2.x format (with callback_api_version)
+            self.client = mqtt.Client(
+                callback_api_version=mqtt.CallbackAPIVersion.VERSION1,
+                client_id=config.MQTT_CLIENT_ID
+            )
+        except (TypeError, AttributeError):
+            # Fall back to v1.x format
+            self.client = mqtt.Client(config.MQTT_CLIENT_ID)
         
         # Set credentials if provided
         if config.MQTT_USER and config.MQTT_PASSWORD: