librespot: switch from cross-compile to native ARM64 build

Cross-compile on x86_64 with qemu emulation takes >30min and hits
60-90min ceiling due to slow crate-by-crate aarch64 build under qemu.
Native ARM64 build on RPi 3B+ with --jobs 2 (1GB RAM) is much faster.

Rust 1.85.1 installed via rustup on RPi (precompiled aarch64 toolchain).

infra/librespot/Dockerfile

@@ -1,51 +1,43 @@
 # Librespot (Spotify Connect) for ARM64
-# Multi-stage: cross-compile Rust app on x86_64 builder, ship slim runtime.
-# Audio output: PulseAudio (connect to audio-bridge via TCP localhost:4713).
+# Multi-stage Docker build. Run on ARM64 host (RPi 3B+ etc).
+# Audio output: PulseAudio (connects to audio-bridge via TCP localhost:4713).
 
 FROM rust:1.85.1-bookworm AS builder
 
-# Cross-compile toolchain for aarch64
-RUN rustup target add aarch64-unknown-linux-gnu
-RUN dpkg --add-architecture arm64 \
- && apt-get update \
+RUN apt-get update \
  && apt-get install -y --no-install-recommends \
-      gcc-aarch64-linux-gnu \
-      libpulse-dev:arm64 \
-      libasound2-dev:arm64 \
-      libssl-dev:arm64 \
+      libpulse-dev \
+      libasound2-dev \
  && rm -rf /var/lib/apt/lists/*
 
-# Build librespot. Pin to a known tag.
 ARG LIBRESPOT_VERSION=v0.8.0
 RUN git clone --depth 1 --branch ${LIBRESPOT_VERSION} \
         https://github.com/librespot-org/librespot.git /src
 WORKDIR /src
-ENV CARGO_TARGET_AARCH64_UNKNOWN_LINUX_GNU_LINKER=aarch64-linux-gnu-gcc
-RUN cargo build --release --target aarch64-unknown-linux-gnu --no-default-features --features="pulseaudio-backend"
+
+# Limit parallelism to 2 (RPi 3B+ has 4 cores but only 1GB RAM).
+# Lower = less memory pressure, slower build. Higher = OOM risk.
+RUN cargo build --release --jobs 2 \
+    --no-default-features \
+    --features="pulseaudio-backend"
 
 FROM debian:bookworm-slim
 
-RUN dpkg --add-architecture arm64 \
- && apt-get update \
+RUN apt-get update \
  && apt-get install -y --no-install-recommends \
       ca-certificates \
-      libpulse0:arm64 \
-      libasound2:arm64 \
-      libssl3:arm64 \
+      libpulse0 \
+      libasound2 \
  && rm -rf /var/lib/apt/lists/*
 
-COPY --from=builder /src/target/aarch64-unknown-linux-gnu/release/librespot /usr/local/bin/librespot
+COPY --from=builder /src/target/release/librespot /usr/local/bin/librespot
 
-# Cache dir for Spotify credentials
 VOLUME ["/var/cache/librespot"]
-
-# PulseAudio bridge is at localhost:4713 (audio-bridge)
 ENV PULSE_SERVER=tcp:127.0.0.1:4713
 
 CMD ["librespot", \
      "--name", "Klubhaus", \
      "--backend", "pulseaudio", \
-     "--device", "alsa_output.default", \
      "--bitrate", "320", \
      "--enable-audio-cache", \
      "--cache", "/var/cache/librespot"]