use tmpfile demo db

src/main.rs

@@ -92,7 +92,15 @@ fn rocket() -> _ {
     let args = Args::parse();
 
     let db_url = if args.demo {
-        "file:memdb1?mode=memory&cache=shared".to_string()
+        // Use a temporary file for demo mode instead of in-memory database
+        let temp_db = "/tmp/rss-reader-temp-db.sqlite";
+        // Delete the file if it exists to start fresh
+        if std::path::Path::new(temp_db).exists() {
+            std::fs::remove_file(temp_db).expect("Failed to remove old temporary database");
+        }
+        // Create the new database file
+        std::fs::File::create(temp_db).expect("Failed to create temporary database file");
+        format!("sqlite:{}", temp_db)
     } else {
         let database = args
             .database