chore(fleet): repoint stale irv-ml1 refs (10.100.79.3 -> irv-ml1.nh3.internal)

The 2026-09-06 headscale cutover retired irv-ml1's wg0 tunnel IP 10.100.79.3
(now 10.6.110.50). Repointed all LIVE canonical refs to the DNS NAME so the next
move can't re-break them: homepage.href/siteMonitor labels across 25 stack
composes, load-bearing env defaults (asset-engine INFERENCE_HOST, open-webui
AUDIO_TTS_OPENAI_API_BASE_URL, skaldsong SKALDSONG_TTS_BASE_URL, zonos-gateway
ZONOS_URL, dia), homepage services.yaml manual cards (Voice Design Studio,
IRV-ML1), and servers/irv-ml1/ssh-target. Updated the stale 'WG tunnel' comment
to the mesh reality.

Left as-is: README curl-examples and .env.example comments (docs), and historical
mentions in CLAUDE.md/persistent-memory. NOTE: applying the label repoints to the
RUNNING irv-ml1 containers needs a recreate per service (labels read at creation);
deployed .env values are separate from these canonical defaults.

stacks/skaldsong/compose.yaml

@@ -71,7 +71,7 @@ services:
       # TTS — Kokoro on irv-ml1, reached over WireGuard via ana-wg from
       # ana-docker. Same URL works fleet-wide.
       SKALDSONG_TTS_ENGINE: "${SKALDSONG_TTS_ENGINE:-kokoro}"
-      SKALDSONG_TTS_BASE_URL: "${SKALDSONG_TTS_BASE_URL:-http://10.100.79.3:8193}"
+      SKALDSONG_TTS_BASE_URL: "${SKALDSONG_TTS_BASE_URL:-http://irv-ml1.nh3.internal:8193}"
 
       # VibeVoice secondary TTS engine (issue #73, added 2026-05-27).
       # Same fleet (irv-ml1) as Kokoro, separate port 8194. Encode-once