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>

docker/nmsr/Dockerfile

@@ -0,0 +1,33 @@
+# NMSR-as-a-Service (https://github.com/NickAcPT/nmsr-rs) — built from source.
+# Upstream ships no published image, so we vendor a pinned build. Adapted from
+# the upstream Dockerfile but: pinned to a commit (reproducible), and the config
+# is bind-mounted at runtime (not COPYed) so it can change without a rebuild.
+#
+# Pin — bump deliberately:
+ARG NMSR_REF=948ba4bc027b
+
+FROM rust:slim-bookworm AS builder
+ARG NMSR_REF
+WORKDIR /tmp
+RUN apt-get update -y \
+ && apt-get --no-install-recommends install -y git libssl-dev pkg-config ca-certificates
+RUN git clone https://github.com/NickAcPT/nmsr-rs/
+WORKDIR /tmp/nmsr-rs
+RUN git checkout "${NMSR_REF}"
+# target-cpu=native: this image is built on the host that runs it (self-host).
+RUN RUSTFLAGS="-Ctarget-cpu=native" \
+    cargo build --release --bin nmsr-aas --features ears --package nmsr-aas
+
+FROM rust:slim-bookworm
+# mesa-vulkan-drivers provides lavapipe (software Vulkan) for headless rendering.
+RUN apt-get update -y \
+ && apt-get --no-install-recommends install -y mesa-vulkan-drivers ca-certificates
+WORKDIR /nmsr
+COPY --from=builder /tmp/nmsr-rs/target/release/nmsr-aas /nmsr/nmsr-aas
+ENV NMSR_USE_SMAA=1 \
+    NMSR_SAMPLE_COUNT=1 \
+    WGPU_BACKEND=vulkan \
+    RUST_BACKTRACE=1
+EXPOSE 8080
+# config.toml is bind-mounted by docker-compose.nmsr.yml.
+CMD ["/nmsr/nmsr-aas", "-c", "/nmsr/config.toml"]