feat(scraper): implement CloakBrowser support and enhance request stealth

Integrate CloakBrowser to improve success rates against Cloudflare
challenges and implement more robust request handling in the Go backend.

- Add CloakBrowser integration to Dockerfile and requirements
- Implement domain-specific request semaphores in Go to prevent rate-limiting
- Add shared HTTP client with cookie jar and header preservation for
  better session management
- Enhance request headers in Go to include modern client hints (Sec-Ch-Ua)
- Add benchmarking scripts to compare fetch methods (urllib vs Scrapling
  vs CloakBrowser)
- Update docker-compose to support CloakBrowser environment variables
- Optimize Docker image by pre-downloading patched Chromium binaries

Dockerfile

@@ -31,6 +31,10 @@ RUN pip install --no-cache-dir -r requirements-scrapling.txt
 # Install Playwright browsers with deps in one layer
 RUN playwright install chromium --with-deps
 
+# Pre-download CloakBrowser patched Chromium binary so it doesn't
+# download at runtime (saves ~10-20s per cold-start request).
+RUN python -m cloakbrowser install
+
 # Fix Python symlinks
 RUN ln -sf /usr/local/bin/python /opt/scrapling/bin/python \
     && ln -sf /usr/local/bin/python /opt/scrapling/bin/python3
@@ -50,6 +54,8 @@ RUN apt-get update && apt-get install -y --no-install-recommends \
     libxkbcommon0 libatspi2.0-0 libx11-6 libxcomposite1 libxdamage1 \
     libxext6 libxfixes3 libxrandr2 libgbm1 libcairo2 libpango-1.0-0 \
     libasound2 \
+    fonts-liberation fonts-noto-color-emoji fonts-noto-core \
+    fontconfig locales \
     && rm -rf /var/lib/apt/lists/*
 
 # Create non-root user
@@ -64,10 +70,14 @@ COPY --from=python-builder /opt/scrapling /opt/scrapling
 # Copy Playwright browser cache
 COPY --from=python-builder /root/.cache/ms-playwright /home/scraper/.cache/ms-playwright
 
-# Copy scrapling script
-COPY scripts/scrapling_fetch.py /opt/scrapling/scripts/scrapling_fetch.py
+# Copy CloakBrowser patched Chromium binary cache
+COPY --from=python-builder /root/.cloakbrowser /home/scraper/.cloakbrowser
 
-# Create cache directory for Playwright
+# Copy scrapling and cloakbrowser scripts
+COPY scripts/scrapling_fetch.py /opt/scrapling/scripts/scrapling_fetch.py
+COPY scripts/cloakbrowser_fetch.py /opt/scrapling/scripts/cloakbrowser_fetch.py
+
+# Create cache directory and fix permissions
 RUN mkdir -p /home/scraper/.cache && chown -R scraper:scraper /home/scraper /opt/scrapling
 
 USER scraper