fix: use dot instead of colon for microsecond separator of last_replaced in strftime (Python 3.14 compatibility)

[rtasarz]

Python 3.14 datetime.fromisoformat() became stricter and no longer accepts microsecond part with colon (:%f).
Changed to dot separator (.%f) to restore compatibility.

Solves following exception, that prevents Battery Notes to initialize:

ERROR (MainThread) [homeassistant.config_entries] Error setting up entry Battery Notes for battery_notes
Traceback (most recent call last):
File "/srv/homeassistant/lib/python3.14/site-packages/homeassistant/config_entries.py", line 762, in __async_setup_with_context
result = await component.async_setup_entry(hass, self)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
File "/home/ha/.homeassistant/custom_components/battery_notes/init.py", line 176, in async_setup_entry
coordinator = BatteryNotesSubentryCoordinator(hass, config_entry, subentry)
File "/home/ha/.homeassistant/custom_components/battery_notes/coordinator.py", line 209, in init
self.last_replaced = datetime.fromisoformat(last_replaced)
~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^
ValueError: Invalid isoformat string: '2026-01-26T17:34:28:192804'

[andrew-codechimp]

Thanks for pointing this out, would have taken me a while to track that one down.
Lint issue is my doing so all good :smiling

Just released 3.3.1 to beta with this fix in it.