Add comprehensive SEO improvements: meta tags, robots.txt, sitemap.xml, and favicon. Fix meta description rendering issues with proper HTML entity encoding. Update port configuration to use PORT environment variable.

FAVICON_CREATION.md

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+# Favicon Creation Guide
+
+This document explains how to create a proper favicon from the 📈 emoji for the Markov Economics application.
+
+## Recommended Approach
+
+To create a professional favicon from the 📈 emoji, follow these steps:
+
+1. Use a graphic design tool like:
+   - Adobe Illustrator or Photoshop
+   - Free tools like GIMP or Inkscape
+   - Online favicon generators
+
+2. Create a 16x16 pixel and 32x32 pixel version of the favicon with the 📈 symbol
+
+3. Export in PNG and ICO formats
+
+## Alternative: Using Online Tools
+
+1. Visit a favicon generator site like favicon.io or realfavicongenerator.net
+2. Upload an image of the 📈 emoji or use their emoji tool
+3. Generate the favicon package
+4. Replace the placeholder files in the `app/static/img/` directory with the generated files
+
+## SVG Version
+
+We've included an SVG version that renders the emoji directly:
+- File: `app/static/img/favicon.svg`
+
+This works in modern browsers but may not be supported in all contexts where favicons are used.
+
+## Implementation Notes
+
+The HTML already includes references to all favicon versions:
+- SVG version (modern browsers)
+- PNG versions (32x32 and 16x16)
+- Apple touch icon