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.

app/routes/main.py

@@ -256,6 +256,30 @@ def health_check():
     })
 
 
+@main_bp.route('/robots.txt')
+def robots_txt():
+    """
+    Serve the robots.txt file.
+    
+    Returns:
+        robots.txt content
+    """
+    from flask import current_app
+    return current_app.send_static_file('robots.txt')
+
+
+@main_bp.route('/sitemap.xml')
+def sitemap_xml():
+    """
+    Serve the sitemap.xml file.
+    
+    Returns:
+        sitemap.xml content
+    """
+    from flask import current_app
+    return current_app.send_static_file('sitemap.xml')
+
+
 @main_bp.errorhandler(404)
 def not_found_error(error):
     """