Add comments, social sharing, SEO, and quick mobile nav fix

[Phinart98]

Add these finishing touches to make the blog fully largely feature-complete:

1. Giscus Comments Integration

• Add the Giscus script to blog_page.html and event_page.html (replace the comment placeholders at blog_page.html:71 and event_page.html:95)
• Only show when page.enable_comments == True
• We'll need to get the Giscus config (repo_id, category_id) from the Jekyll _config.yml file

2. Social Sharing Buttons

• Add share buttons below article content: Twitter, LinkedIn, Mastodon, Email, Copy Link
• Use native share URLs (no external libraries)
• Style with Tailwind and Font Awesome icons

3. Quick Fix: Mobile Nav

• Fix the missing /events/ path in mobile menu