v0.7.0

• Lighting convenience layer: device on / off / toggle / brightness / color / color-temp. Until now the only way to drive a bulb was hand-writing a
  device set payload (device set 'Lounge Lamp' state=ON brightness=128) or
  a raw device write on the genOnOff/genLevelCtrl clusters. The new
  shortcuts cover the everyday cases with validated arguments:
  • device on <name> [--transition S] / device off / device toggle
    publish {"state": "ON" | "OFF" | "TOGGLE"}.
  • device brightness <name> 0-254 [--transition S] — the standard Zigbee
    range; 255 is rejected ("max" is not a settable level on z2m).
  • device color <name> red | #ff8800 | '255,136,0' [--transition S] —
    named colors, hex or RGB triples, all normalised to the
    {"color": {"r","g","b"}} object z2m expects.
  • device color-temp <name> <mireds> [--kelvin] [--transition S] — mireds
    150-500 (lower = cooler); --kelvin converts (e.g. 2700 --kelvin →
    color_temp 370).
    All six resolve IEEE addresses to friendly names first (same as
    device identify), so device toggle 0xa4c138… works, and an unknown
    device aborts instead of publishing to a nonexistent topic. Payloads are
    validated BEFORE any MQTT connection is opened — device brightness <name> 255 reports "brightness must be between 0 and 254" rather than a broker
    connection error. Output is {"friendly_name", "topic", "published", "rc"} (same shape as device identify); like device set there is no
    bridge/response, so confirm with device state <name>. Room-wide changes
    still belong in a group set groupcast.
• Core functions light_payload, set_light, parse_color,
  kelvin_to_mireds, check_brightness, check_color_temp,
  check_transition in core/devices.py.
• Why it matters: device find --capability brightness → device brightness <name> 128 is now a two-command light-dimming one-liner instead of
  property-name archaeology.
• 53 new tests (34 unit + 19 E2E/workflow); total suite 976 passed, gate
  green (coverage 99.3%, ruff check/format clean, bandit clean).