fix: add smbus2 dependency, i2c-tools, and use hex I2C addresses in docs

- Add smbus2>=0.4.0 to pyproject.toml core dependencies so it is always
  present in the venv rather than relying on runtime auto-install
- Add i2c-tools to apt-get installs in both install and upgrade paths
  so /dev/i2c-* devices are accessible and i2cdetect is available for
  diagnostics (service user was already being added to the i2c group)
- Switch ENS210 config examples to hex I2C address notation (0x43) to
  match datasheets and i2cdetect output; update contributor docs guidance
  accordingly

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

config.yaml.example

@@ -242,7 +242,7 @@ sensors:
     #   enabled: true
     #   auto_install_packages: true
     #   settings:
-    #     i2c_address: 67       # 0x43 in decimal (default ENS210 address)
+    #     i2c_address: 0x43     # Default ENS210 address
     #     bus_number: 1         # I2C bus number (1 for Raspberry Pi default)
     #     read_timeout_seconds: 1.0  # Max seconds to wait for valid data (polls every 50 ms)
 

docs/adding_sensors.md

@@ -107,7 +107,7 @@ Find the `sensors.definitions` block and add your sensor alongside the existing
     #     some_option: value
 ```
 
-Use decimal for numeric config values that would naturally be written in hex (e.g. I2C addresses: `0x43` = `67`). Add a comment showing both forms if the value is commonly written in hex.
+Use hex notation for I2C addresses (e.g. `0x43`) as this matches how addresses are listed in datasheets and tools like `i2cdetect`.
 
 ### 3. Test locally
 

manage.sh

@@ -341,7 +341,7 @@ install_repeater() {
 
     echo "25"; echo "# Installing system dependencies..."
     apt-get update -qq
-    DEBIAN_FRONTEND=noninteractive apt-get install -y libffi-dev libusb-1.0-0 sudo jq pip python3-venv python3-rrdtool wget swig build-essential python3-dev
+    DEBIAN_FRONTEND=noninteractive apt-get install -y libffi-dev libusb-1.0-0 sudo jq pip python3-venv python3-rrdtool wget swig build-essential python3-dev i2c-tools
     # Install polkit (package name varies by distro version)
     DEBIAN_FRONTEND=noninteractive apt-get install -y policykit-1 2>/dev/null \
         || DEBIAN_FRONTEND=noninteractive apt-get install -y polkitd pkexec 2>/dev/null \
@@ -746,7 +746,7 @@ upgrade_repeater() {
         echo "[3/9] Updating system dependencies..."
         apt-get update -qq
 
-        apt-get install -y libffi-dev libusb-1.0-0 sudo jq pip python3-venv python3-rrdtool wget swig build-essential python3-dev
+        apt-get install -y libffi-dev libusb-1.0-0 sudo jq pip python3-venv python3-rrdtool wget swig build-essential python3-dev i2c-tools
         # Install polkit (package name varies by distro version)
         apt-get install -y policykit-1 2>/dev/null \
             || apt-get install -y polkitd pkexec 2>/dev/null \

pyproject.toml

@@ -39,6 +39,7 @@ dependencies = [
     "pyserial>=3.5",
     "pyjwt>=2.8.0",
     "ws4py>=0.6.0",
+    "smbus2>=0.4.0",
 ]