fix(parser): accept numeric journalctl timezones

[stacknil]

Summary

• fix journalctl numeric timezone parsing so documented +HHMM / +HH:MM offsets are accepted
• add parser coverage for compact positive and colon negative offsets, including UTC normalization expectations

Validation

• & 'C:\Program Files (x86)\Microsoft Visual Studio\18\BuildTools\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\cmake.exe' --build build --config Debug --target test_parser
• & 'C:\Program Files (x86)\Microsoft Visual Studio\18\BuildTools\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\ctest.exe' --test-dir build -C Debug -R parser --output-on-failure
• & 'C:\Program Files (x86)\Microsoft Visual Studio\18\BuildTools\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\cmake.exe' --build build --config Debug
• & 'C:\Program Files (x86)\Microsoft Visual Studio\18\BuildTools\Common7\IDE\CommonExtensions\Microsoft\CMake\CMake\bin\ctest.exe' --test-dir build -C Debug --output-on-failure