Fix OptionsFlow crash on HA 2024.x+ (config_entry no longer settable in __init__)

[schizek]

HA 2024.x made config_entry a read-only property on the OptionsFlow base class. This integration was still assigning to it in __init__, which caused a crash every time the options dialog was opened:

AttributeError: property 'config_entry' of 'VictorSmartKillOptionsFlowHandler' object has no setter

Changes:

• config_flow.py: Removed VictorSmartKillOptionsFlowHandler.__init__ and updated async_get_options_flow to call the handler with no arguments. async_step_user now reads self.config_entry.options directly via the base class property.
• __init__.py: Changed raise UpdateFailed(exception) to raise UpdateFailed(repr(exception)) so error messages in the log are never silently blank when the exception's __str__ returns an empty string.

Tested on HA 2025.1 with Python 3.14.