## Description
<!-- Describe the changes in detail -->
The clock ignored the device's system 24-hour preference:
getTimeFormatter derived 12/24h purely from the locale. This reads
DateFormat.is24HourFormat and builds the time pattern from it, so the
clock follows the system setting.
### Related issues
<!-- If this is a new feature or a change, there must be a discussion in
an issue first, reference the issue here -->
<!-- If fixing a bug, reference the bug issue here, or describe the bug,
including steps to reproduce -->
### Testing
<!-- Describe how this change was tested and on what device(s) -->
Tested on the emulator toggling the system 24-hour setting on/off.
assembleDefaultDebug, testDefaultDebugUnitTest and pre-commit (ktlint)
pass.
## Screenshots
<!-- Please include screenshots if the PR alters any UI elements -->
## AI or LLM usage
<!-- If you used any AI or LLM assistance, please list where in the code
and how you tested it -->
The analysis and the fix were done by me with AI assistance (Claude). I
wrote the description myself; the English wording was polished with AI.
I understand the code and can maintain it.
8a684545ac