Keep the API DeviceInfo compilation_time field using the old
get_compilation_time_ref() format for backward compatibility.
The text sensor build_time_str continues to use the new ISO 8601 format.
Change the API's DeviceInfo response to use the new ISO 8601 format
with timezone for compilation_time field by calling get_build_time_string()
instead of get_compilation_time_ref().
Update the placeholder build_info_data.h to match the new format.
Update integration test to expect the new format for compilation_time.
Use YYYY-MM-DD HH:MM:SS +ZZZZ format instead of the locale-dependent
'%b %d %Y, %H:%M:%S' format. This provides:
- Unambiguous date format (YYYY-MM-DD)
- Timezone information
- Locale-independent formatting
- Better sortability and parseability
Example: "2025-12-15 16:30:27 +0000" instead of "Dec 15 2025, 16:30:27"
Tests validate the format using strptime with '%Y-%m-%d %H:%M:%S %z'.
