fix: normalize range validation for light, cover, and valve domains

[Faerkeren]

Closes #75

Issue validity

Valid and actionable. Four public action methods had inconsistent or missing numeric range validation, making the client's behaviour unpredictable and pushing input checking onto callers.

Method	Documented range	Old behaviour	New behaviour
light.set_brightness	0–255	int() coerce only, no range check	Raises ValueError outside 0–255
light.set_rgb	each component 0–255	no coerce, no range check	Raises ValueError for any component outside 0–255
cover.set_position	0–100	int() coerce only (docstring said "clamped")	Raises ValueError outside 0–100
valve.set_position	0–100	no range check at all	Raises ValueError outside 0–100; validation runs before feature-support guard

fan.set_percentage, humidifier.set_humidity, and media_player.set_volume already validated correctly and are unchanged.

Fix

• Added src/haclient/domains/_utils.py with a single shared helper:

  def validate_range(value: int, lo: int, hi: int, name: str) -> int

  Coerces to int, checks the closed interval, and raises ValueError with a consistent message ("{name} must be between {lo} and {hi}, got {value}").

• Applied to light.set_brightness, light.set_rgb (all three components), cover.set_position, and valve.set_position.

• Docstrings updated with explicit Raises sections where missing.

Tests

Four new test functions added to tests/test_domains.py:

• test_light_set_brightness_validation — below-range, above-range, boundary (0, 255)
• test_light_set_rgb_validation — below/above range for each of r, g, b; boundaries (0,0,0) and (255,255,255)
• test_cover_set_position_validation — below-range, above-range, boundary (0, 100)
• test_valve_set_position_validation — range validation fires even when feature is absent; boundaries dispatched when feature is present

Checks run

• pytest: 311 passed, coverage 97.17% (threshold 95%)
• ruff check + ruff format --check: all passed
• mypy src: no issues