Preserve dots in Asuswrt-Merlin custom client names

[maghuro]

Summary

Preserve Asuswrt-Merlin custom_clientlist display names verbatim instead of passing them through normalizeHostname.

Problem

Merlin's custom_clientlist contains user-defined friendly names, not DNS hostnames.

Applying normalizeHostname truncates any name at the first dot because the helper assumes the remainder is a DNS suffix.

For example:

Device 2.5Gbps

is currently exposed as:

Device 2

Fix

Use the custom_clientlist display name as-is in the Merlin client-info discovery path.

Other discovery sources continue to use normalizeHostname where stripping DNS suffixes is appropriate.

Validation

Added a regression test covering a dotted Merlin friendly name using synthetic data.

This targets the maintained v1.0 line.