URL Extractor per Libor Benes (Dr. B)

Extract URLs from <a> tags (href attributes) and plain text. The Add-On may not extract URLs from scripts, styles, or non-visible elements.

Designed for Security:
• Minimal permissions (activeTab only), safe DOM methods, validated URL extraction.
• Strict Content Security Policy restricts scripts and styles to local files.
• Local extraction logic with no network requests, storage, or external dependencies.