Fix anonymous access 500 error and add environment variable control

- Fixed dashboard.html template error accessing current_user.username for anonymous users
- Added ALLOW_ANONYMOUS_ACCESS environment variable with default true
- Enhanced index route logic to properly check config before allowing anonymous access
- Added proper environment variable to docker-compose.yml
- Anonymous access now works without 500 server errors

Fixes issue #2 completely - anonymous access is now functional

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

templates/post_detail.html

@@ -654,6 +654,10 @@ function sharePost() {
 }
 
 function savePost() {
+    // TODO: Implement save post functionality
+    // User can save posts to their profile for later viewing
+    // This needs database backend integration with user_saved_posts table
+    // Same implementation needed as dashboard.html savePost function
     alert('Save functionality coming soon!');
 }