feat: resolve .numa services to LAN IP for remote clients (#23)

* feat: resolve .numa services to LAN IP for remote clients

Remote DNS clients (e.g. phones on same WiFi) received 127.0.0.1 for
local .numa services, which is unreachable from their perspective.
Now returns the host's LAN IP when the query originates from a
non-loopback address. Also auto-widens proxy bind to 0.0.0.0 when
DNS is already public, and adds a startup warning when the proxy
remains localhost-only.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: respect proxy bind_addr config, don't auto-widen

The auto-widen silently overrode an explicit config value — the user's
config should be the source of truth. Now the proxy always uses the
configured bind_addr, and the warning fires whenever it's 127.0.0.1.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* docs: update proxy bind_addr comment in example config

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

numa.toml

@@ -54,7 +54,7 @@ enabled = true
 port = 80
 tls_port = 443
 tld = "numa"
-# bind_addr = "127.0.0.1"  # default; auto 0.0.0.0 when [lan] enabled
+# bind_addr = "127.0.0.1"  # default; set to "0.0.0.0" for LAN access to .numa services
 
 # Pre-configured services (numa.numa is always added automatically)
 # [[services]]