Add AgentCPM preset and fix host picker

[MilitantTurtle]

What changed

• Add an explicit reference preset for OpenBMB AgentCPM Explore.
• Make the native GGUF picker recognize a browser using the Launchpad host's own LAN address without hardcoding interface IPs.
• Add regression coverage for matching connection endpoints, IPv4-mapped IPv6, remote LAN clients, and request-handler wiring.

Why

The picker previously relied on hostname resolution to enumerate local addresses. On multi-adapter Windows hosts, that lookup can temporarily omit an active interface, causing a same-machine request through the host's LAN URL to receive 403.

The new check compares the normalized request peer address with the accepted socket's local endpoint, while retaining loopback and hostname-resolution fallbacks. A different LAN client remains unable to summon a dialog on the host.

AgentCPM Explore does not publish a complete sampling preset, so its profile is explicitly marked as a Qwen base-model reference rather than a creator-documented preset.

Validation

• python -m unittest discover -s tests -v — 27 passed
• python -m py_compile app.py setup.py
• node --check static/app.js
• node --check static/settings.js
• git diff --check
• Tracked-file scan found no private machine paths, stored credentials, secrets, logs, or runtime state