Add webpage screenshot capture with Playwright

Implements automated screenshot capture for all discovered HTTP/HTTPS services using Playwright with headless Chromium. Screenshots are saved as PNG files and referenced in JSON reports.

Features:
- Separate ScreenshotCapture module for code organization
- Viewport screenshots (1280x720) with 15-second timeout
- Graceful handling of self-signed certificates
- Browser reuse for optimal performance
- Screenshots stored in timestamped directories
- Comprehensive documentation in README.md and new CLAUDE.md

Technical changes:
- Added src/screenshot_capture.py: Screenshot capture module with context manager pattern
- Updated src/scanner.py: Integrated screenshot capture into HTTP/HTTPS analysis phase
- Updated Dockerfile: Added Chromium and Playwright browser installation
- Updated requirements.txt: Added playwright==1.40.0
- Added CLAUDE.md: Developer documentation and implementation guide
- Updated README.md: Enhanced features section, added screenshot details and troubleshooting
- Updated .gitignore: Ignore entire output/ directory including screenshots

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Dockerfile

@@ -7,6 +7,8 @@ RUN apt-get update && \
     build-essential \
     libpcap-dev \
     nmap \
+    chromium \
+    chromium-driver \
     && rm -rf /var/lib/apt/lists/*
 
 # Build and install masscan from source
@@ -24,6 +26,10 @@ WORKDIR /app
 COPY requirements.txt .
 RUN pip install --no-cache-dir -r requirements.txt
 
+# Install Playwright browsers (Chromium only)
+# Note: We skip --with-deps since we already installed system chromium and dependencies above
+RUN playwright install chromium
+
 # Copy application code
 COPY src/ ./src/