Fixed state inconsistencies during auth errors:
Bug #4: tomorrow_data_available incorrectly returns True during auth failure
- Now returns None (unknown) when coordinator.last_exception is ConfigEntryAuthFailed
- Prevents misleading "data available" when API connection lost
Bug #5: Sensor states inconsistent during error conditions
- connection: False during auth error (even with cached data)
- tomorrow_data_available: None during auth error (cannot verify)
- lifecycle_status: "error" during auth error
Changes:
- binary_sensor/core.py: Check last_exception before evaluating tomorrow data
- tests: 25 integration tests covering all error scenarios
Impact: All three sensors show consistent states during auth errors,
API timeouts, and normal operation. No misleading "available" status
when connection is lost.
