v2.3.0-beta.1 – SOC bounds fix, plug helper refactor

v2.3.0-beta.1 – Pre-release for testing

This pre-release is intended for HACS beta testing before promoting to a stable release.
Enable "Show beta versions" in HACS → Integrations → Jackery SolarVault → (gear icon) to install.

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Fixed

• SOC Charge Limit slider range corrected to 50–100 % (device enforces minimum 50 %;
  previously the slider allowed 0–100 %, but values below 50 % were silently ignored).
  Confirmed identical on SolarVault 3 and SolarVault 3 Pro Max.

• SOC Discharge Limit slider range corrected to 5–49 % (device enforces maximum 49 %;
  previously the slider allowed 0–100 %, but values above 49 % were silently ignored).

• Smart plug switch creation filter tightened: switches are now only created for
  devType=6 (smart plugs). The previous check (devType != 2) would incorrectly have
  created switches for CT devices or collectors if they appeared in the subdevice list.

Added

• Dynamic SOC limit bounds: When the device reports minSocChg/maxSocChg/minSocDischg/
  maxSocDischg fields, the slider min/max values update automatically to reflect device-reported
  limits (adopted from upstream).

Refactored

• Plug helper functions (plug_comm_mode, plug_mqtt_control_allowed, should_create_plug_switch,
  COMM_MODE_LABELS, COMM_MODE_LOCAL, COMM_MODE_CLOUD) moved from switch.py to sensor.py
  as shared public exports. switch.py now imports from sensor.py instead of maintaining
  private duplicates.

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Test coverage: 87 tests, 53.72 % coverage