feat(devices): add Cast LB500 series self-cleaning cat litter box

[samclark2015]

Adds support for the Cast LB500 series self-cleaning cat litter box (LB500A, LB500C, also sold under the UPFAS brand).

Product ID: frho2xmkraxldtwo

Entities:

• Status sensor (idle/smoothing/cleaning)
• Cat weight, last visit weight, last visit duration (all in lb / seconds)
• Visits today (live) and visits yesterday (end-of-day snapshot)
• Fault binary_sensor with descriptions (drum not installed, overload)
• No-cat-detected binary_sensor (24h notification)
• Clean now and Cancel buttons
• Auto-clean switch
• Config selects: clean delay (10–120 s), minimum visit time (10–30 s), cleaning cycles (1–2), minimum cat weight (3.3–3.9 lb)

The device reports weights only in pounds (there is no unit selector DP). DPS 105 ("timerclean", labeled "Regular Clean" in the app) was tested and triggers the same clean cycle as DPS 102, so it is intentionally not exposed as a separate button.