Add a comprehensive LegalDocument base class in mywebdav/legal.py with abstract methods for title and content generation, along with full markdown and HTML implementations for compliance statement, contact/complaint mechanism, and cookie policy pages, replacing placeholder content with detailed regulatory and procedural information.
Replace all eight footer legal links from .md to .html extensions in mywebdav-app.js and create corresponding HTML documents for privacy policy, data processing agreement, terms of service, cookie policy, security policy, compliance statement, data portability & deletion policy, and contact & complaint mechanism, each with placeholder content and back navigation.
