feat(books): add read-aloud generation

Generate a synced read-aloud EPUB from a book's EPUB and audiobook through an
optional STAlign worker (Docker on CPU, or native with MLX on Apple Silicon),
with review, re-sync, replace in place, restart recovery and live progress on
the Files tab. Book details also stack the ebook and audiobook covers when
both exist. See docs/READ_ALOUD.md.

workers/read-aloud/Dockerfile

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+# Debian trixie for ffmpeg 7: STAlign's audiobook probe passes `ffprobe -output_format`, which the
+# ffmpeg 5.1 in bookworm rejects, failing every job in its first stage.
+ARG NODE_IMAGE=node:26.8.1-trixie-slim
+
+FROM ${NODE_IMAGE} AS builder
+WORKDIR /app
+RUN npm install -g pnpm@11.22.0
+
+# The image runs on CPU only: without this, onnxruntime-node downloads its CUDA provider on
+# linux/x64, which cannot load here (no CUDA or cuDNN libraries) and only adds size.
+ENV ONNXRUNTIME_NODE_INSTALL=skip
+
+COPY package.json pnpm-workspace.yaml pnpm-lock.yaml ./
+COPY patches/ ./patches/
+COPY packages/types/package.json ./packages/types/
+COPY workers/read-aloud/package.json ./workers/read-aloud/
+RUN --mount=type=cache,id=pnpm-read-aloud,target=/root/.local/share/pnpm/store \
+    pnpm install --filter @bookorbit/read-aloud-worker... --frozen-lockfile
+
+COPY packages/types/ ./packages/types/
+COPY workers/read-aloud/ ./workers/read-aloud/
+RUN pnpm --config.verify-deps-before-run=false --filter @bookorbit/types build && \
+    pnpm --config.verify-deps-before-run=false --filter @bookorbit/read-aloud-worker build && \
+    pnpm --config.allow-unused-patches=true --filter @bookorbit/read-aloud-worker deploy --prod --legacy /deploy && \
+    rm -rf /deploy/dist /deploy/assets && \
+    cp -r /app/workers/read-aloud/dist /app/workers/read-aloud/assets /deploy/ && \
+    types_dir="$(dirname "$(cd /deploy && node -p 'require.resolve("@bookorbit/types/package.json")')")" && \
+    rm -rf "$types_dir/dist" && cp -r /app/packages/types/dist "$types_dir/dist" && \
+    cd /deploy && node -e 'require("@bookorbit/types").READ_ALOUD_WORKER_PROTOCOL || process.exit(1)' && \
+    find node_modules/.pnpm/onnxruntime-node@*/node_modules/onnxruntime-node/bin/napi-v6 -mindepth 1 -maxdepth 1 ! -name linux -exec rm -rf {} +
+
+# Speech models reach the data volume (XDG_DATA_HOME) only through the ghost-story patch; without it
+# they go to the home folder, which is read-only under Compose, and every model download fails.
+RUN cd /deploy && \
+    patched="$(find node_modules/.pnpm -path '*/node_modules/@storyteller-platform/ghost-story/dist/utilities/FileSystem.js')" && \
+    if [ -z "$patched" ] || grep -L 'process.env\["XDG_DATA_HOME"\]' $patched | grep -q .; then \
+      echo "ghost-story in the image lacks patches/@storyteller-platform__ghost-story@0.3.4.patch" >&2; exit 1; \
+    fi
+
+FROM ${NODE_IMAGE} AS runtime
+WORKDIR /app
+RUN apt-get update && \
+    apt-get install -y --no-install-recommends ca-certificates ffmpeg tini && \
+    rm -rf /var/lib/apt/lists/* && \
+    mkdir -p /data/read-aloud/jobs /data/read-aloud/tmp /data/read-aloud/ghost-story && \
+    chown -R node:node /data
+
+ENV NODE_ENV=production
+ENV PORT=8787
+ENV READ_ALOUD_WORKER_HOST=0.0.0.0
+ENV READ_ALOUD_LIBRARY_ROOTS=/books
+ENV READ_ALOUD_WORK_ROOT=/data/read-aloud/jobs
+ENV READ_ALOUD_TMP_DIR=/data/read-aloud/tmp
+ENV READ_ALOUD_CTC_DEVICE=auto
+ENV TMPDIR=/data/read-aloud/tmp
+ENV XDG_DATA_HOME=/data/read-aloud
+
+COPY --from=builder --chown=node:node /deploy ./
+COPY --chown=node:node server/file-env.sh workers/read-aloud/entrypoint.sh ./
+RUN chmod +x /app/entrypoint.sh
+
+# The release this image was built from, reported in health; unset falls back to the package version.
+ARG APP_VERSION
+ENV APP_VERSION=${APP_VERSION}
+
+USER node
+EXPOSE 8787
+ENTRYPOINT ["/usr/bin/tini", "--", "/app/entrypoint.sh"]