Introduce a styles/ plugin package:
- styles/base.py: AlarmStyle ABC (injected set_led, update()->bool contract)
- styles/blink.py: BlinkStyle, the existing count-the-blinks puzzle moved
out of wecker.py's AlarmClock
- styles/simple.py: SimpleStyle, press-once-to-stop (the new default style)
- styles/__init__.py: STYLES registry + get_style() validator + LEGACY_STYLE
wecker.py now resolves the style via the registry and owns only the shared
music/button/cleanup loop; the --style CLI arg defaults to blink so existing
cron entries keep their behaviour. Unknown styles raise before hardware init.
When transitioning from STATE_BLINKING to STATE_WAIT_FOR_INPUT, the script used a stale timestamp `now` from before the blocking `blink_led` function. This caused the puzzle to immediately evaluate as failed. Updated to use `time.time()` after blinking finishes to ensure the user gets the full 3 seconds to enter their answer.