feat(avatar): NMSR skin renderer at avatar.${BASE_DOMAIN}, Drasl-backed

Add NMSR-as-a-Service (NickAcPT/nmsr-rs) rendering players' skins/avatars,
sourced from Drasl instead of Mojang.

- docker/nmsr/Dockerfile     build from source, pinned to commit 948ba4bc027b
                             (ears feature, lavapipe software Vulkan)
- nmsr/config.toml.tmpl       [mojank] -> http://auth.${BASE_DOMAIN}; Drasl
                              serves the Mojang-compatible routes at its bare
                              BaseURL and embeds absolute skin URLs that NMSR
                              fetches directly. allow_offline_mode_uuids=true.
- docker-compose.nmsr.yml     nmsr service (build), host bind 127.0.0.1:9898
                              only, config mount; mounts the caddy avatar snippet
- caddy/conf.d/40-avatar.caddy avatar.${BASE_DOMAIN} -> reverse_proxy nmsr:8080
- nginx-front + LE_SUBDOMAINS  public TLS vhost (HSTS) + cert for avatar
- render-config.sh / .gitignore render + ignore nmsr/config.toml

Skin resolution stays internal over mcnet (caddy alias -> drasl), no public
round-trip.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -5,6 +5,7 @@ runtime/authlib-injector.jar
 
 # rendered configs (from tooling/render-config.sh)
 drasl/config/config.toml
+nmsr/config.toml
 dnsmasq/dnsmasq.conf
 # packwiz pack files rendered from pack/**/*.tmpl by tooling/render-pack.sh
 # (domain-dependent build output); source of truth is the .tmpl + custom/ jars.