fix: purifier light detection and display guards used the wrong state

[ryan-ronnander]

Why

This started with the display switch in Home Assistant failing on my Vital 200S, while the VeSync app changed the same setting without complaint:

ERROR [pyvesync.devices.vesyncpurifier] Cannot set display when light detection is enabled
ERROR [homeassistant.components.websocket_api.http.connection] Error during service call to switch.turn_off: Success

Follow-up to #351. The two guards it added check light_detection_status (whether the room is dark right now) where they mean light_detection_switch (whether the feature is enabled). On a Levoit Vital 200S (LAP-V201S-WUS), that makes light detection and the display unreliable to control through pyvesync, and so through Home Assistant too. I'm preparing a Home Assistant VeSync change that adds a light detection switch and a dark room sensor for these purifiers. With the current guards, that switch silently does nothing when turned on in a dark room, and the existing display switch fails whenever the room is dark.

• toggle_light_detection checked light_detection_status (whether the room is dark right now) where it meant light_detection_switch (whether the feature is enabled). Turning light detection on in a dark room, or off in a lit room, returned True without calling the API.
• toggle_display refused whenever light_detection_status was on, which is the same wrong field. As a result the display switch in HA failed with "Cannot set display when light detection is enabled" depending on how bright the room was.

Fix

• toggle_light_detection compares against light_detection_switch.
• The display guard in toggle_display now applies only to the Vital 100S (LAP-V102S), and checks light_detection_switch. The Vital 200S accepts setDisplay with light detection enabled, and the VeSync app lets you change both settings at any time. The display setting is the master: with light detection on, the device only darkens a display that is set to on while the room is dark.

I kept the guard for the Vital 100S because #351 reported 11017000 BYPASS_NOT_SUPPORTED there, and I don't own a 100S to check. If someone with a 100S finds that it accepts the call, the guard can go.

Only VeSyncAirBaseV2 changes (Vital 100S/200S, Everest Air, Sprout). The Core series and the other purifier classes are untouched.

Tested on hardware

Vital 200S, through Home Assistant with this branch installed. Light detection on, room lit:

• setDisplay off returned success, and the next cloud poll reported display_status: off
• setDisplay on returned success, and the next cloud poll reported display_status: on
• light detection on and off both reach the API regardless of the room reading

Tests

TestAirBaseV2Guards in test_purifiers.py:

• light detection toggles call the API for every combination of switch and room reading
• light detection that is already set skips the API
• toggling with no argument flips the light detection switch, whatever the room reading
• the display toggles with light detection on
• the Vital 100S refuses the display only when the light detection switch is on, whatever the room reading