Fix Python dependencies installation in postinst

- Add requirements.txt to debian/install
- Update postinst to use requirements.txt for pip install
- Install from requirements.txt instead of -e . (editable install)
- Ensures bluepy and paho-mqtt are installed in venv
- Fixes 'ModuleNotFoundError: No module named bluetooth' on startup

debian/postinst

@@ -42,11 +42,19 @@ case "$1" in
             venv/bin/pip install --upgrade pip setuptools wheel
         fi
 
-        # Install Python dependencies from pyproject.toml
+        # Install Python dependencies from requirements.txt
         echo "Installing Python dependencies..."
-        venv/bin/pip install -e . || {
-            echo "Warning: pip install failed. You may need to install dependencies manually."
-        }
+        if [ -f "/opt/sensorpajen/requirements.txt" ]; then
+            venv/bin/pip install -r /opt/sensorpajen/requirements.txt
+        else
+            echo "Warning: requirements.txt not found, installing bluepy and paho-mqtt directly"
+            venv/bin/pip install bluepy paho-mqtt
+        fi
+        
+        if [ $? -ne 0 ]; then
+            echo "Error: Failed to install dependencies"
+            exit 1
+        fi
 
         # Set Bluetooth capabilities on Python executable
         PYTHON_PATH=$(readlink -f /opt/sensorpajen/venv/bin/python3)