feat: self-hosted frontend JS (offline) + docker hardening

- Vendored epub.js/pdf.js+worker/JSZip/DOMPurify in static/vendor/
- reader.html/reader.js servono i JS da /static (niente CDN, offline-ready)
- CSP: rimosse allowlist CDN, aggiunto worker-src 'self' blob:
- Test CSP aggiornati; tutti 16 verdi; verificato smoke test offline in container

Dockerfile

@@ -0,0 +1,52 @@
+FROM python:3.12-slim-bookworm AS builder
+
+WORKDIR /build
+
+COPY requirements.txt requirements.lock ./
+RUN python -m venv /opt/venv \
+    && /opt/venv/bin/pip install --no-cache-dir --upgrade pip \
+    && /opt/venv/bin/pip install --no-cache-dir -r requirements.lock
+
+FROM python:3.12-slim-bookworm AS runtime
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        pandoc \
+        libcairo2 \
+        libpango-1.0-0 \
+        libpangocairo-1.0-0 \
+        libpangoft2-1.0-0 \
+        libharfbuzz0b \
+        libgdk-pixbuf-2.0-0 \
+        libffi8 \
+        shared-mime-info \
+        fonts-dejavu-core \
+        fonts-liberation \
+    && rm -rf /var/lib/apt/lists/*
+
+RUN groupadd --gid 1000 bookish \
+    && useradd --uid 1000 --gid 1000 --create-home --home-dir /home/bookish bookish
+
+COPY --from=builder /opt/venv /opt/venv
+
+WORKDIR /app
+COPY --chown=bookish:bookish app.py config.py gunicorn.conf.py ./
+COPY --chown=bookish:bookish bookish ./bookish
+
+ENV PATH="/opt/venv/bin:$PATH" \
+    PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    BOOKISH_DATA_DIR=/data \
+    BOOKISH_DEBUG=false \
+    PORT=5000
+
+RUN mkdir -p /data/uploads /data/converted \
+    && chown -R bookish:bookish /data /app
+
+USER bookish
+EXPOSE 5000
+VOLUME ["/data"]
+
+HEALTHCHECK --interval=30s --timeout=5s --start-period=20s --retries=3 \
+    CMD python -c "import urllib.request; urllib.request.urlopen('http://127.0.0.1:5000/healthz', timeout=3)"
+
+CMD ["gunicorn", "--config", "gunicorn.conf.py", "app:app"]