Fix Docker Compose for Mac dev mode

- Replace all ghcr.io images (blocked without auth) with local Dockerfiles:
  snapserver/snapclient from debian:bookworm-slim,
  mopidy from debian:bookworm-slim + Python/GStreamer,
  librespot disabled in dev (v0.8.0 has vergen dep bug)
- Fix duplicate 'image' and 'version' keys in compose files
- Dev mode: zones + librespot use alpine dummy containers
- Dashboard dev: use upstream node:20-alpine directly (no custom build)
- Port changed to 8090 (8080 taken by Supabase)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker/librespot/Dockerfile

@@ -0,0 +1,14 @@
+# Stage 1: Build librespot from source
+FROM rust:slim-bookworm AS builder
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends pkg-config libssl-dev \
+    && rm -rf /var/lib/apt/lists/*
+RUN cargo install librespot
+
+# Stage 2: Minimal runtime image
+FROM debian:bookworm-slim
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+COPY --from=builder /usr/local/cargo/bin/librespot /usr/local/bin/librespot
+ENTRYPOINT ["librespot"]