v1.3.0

Release v1.3.0

- bump throws submodule to v1.1.0
- fix CIDR prefix length: it was derived with log2() and was wrong for
  non-byte-aligned masks (/23, /25, ...); count the netmask bits instead
- fetch the IPv4 broadcast address (it was never actually retrieved)
- new convenience API (additive): device::up(), device::has_flag(name|id),
  netinfo::get_device(name), netinfo::has_device(name)
- operator<< uses spaces instead of tabs, so the output is consistent across
  terminals and no longer breaks for long interface names
- guard clean_up() against back() on an empty string; add <cstdint>/<iomanip>
- update GitHub Actions (actions/checkout@v5, create/upload-asset actions @v2)
- document the new API in the README and the example

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Oskari Rauta <oskari.rauta@gmail.com>